Xolair (omalizumab)

Medically Reviewed By Heather Bruce, PharmD

This drug has a boxed warning, the most serious warning from the Food and Drug Administration (FDA). A boxed warning alerts doctors and patients about drug effects that may be dangerous.

It’s possible to develop a serious allergic reaction, called anaphylaxis, from using Xolair. If you develop anaphylaxis, you may experience symptoms such as difficulty breathing, fainting, or swelling of the lips, throat, or tongue.

If you develop any symptoms of anaphylaxis during your treatment with Xolair, go to the hospital or seek emergency care right away. This can be serious and even life threatening. If you develop anaphylaxis to Xolair, your doctor will treat your allergic reaction. Then, they will recommend that you stop using Xolair and try a different medication for your condition.

To learn more, see the “Xolair: Precautions” section below.

About Xolair

Xolair is a brand-name prescription medication. It’s approved by the Food and Drug Administration (FDA) to treat:

Xolair does have some limitations of use. For details about asthma, nasal polyps, CIU and how the drug treats them, see the “Xolair: Uses” section below.

Key points

The following table provides key facts about Xolair.

Active drugomalizumab
Drug classanti-IgE antibody
Formssolution and powder for subcutaneous injection

Finding a healthcare professional

If you’re interested in taking this drug, search here to find a doctor who might prescribe it.

Xolair: Generic or biosimilar

Xolair contains the active drug omalizumab, which is a biologic. It only comes as a brand-name medication. And it isn’t currently available in a biosimilar form.

A biosimilar drug is a medication that is similar to the original biologic drug. Because biologic drugs are made from living cells, they can’t be replicated exactly.

Biosimilar drugs are considered to be just as safe and effective as the brand-name version. Biosimilar drugs usually cost less than brand-name drugs, as well.

Xolair: Side effects

As with most drugs, it’s possible to have side effects with Xolair. These can include some mild side effects but also some serious ones.

To learn more about Xolair’s side effects, talk with your doctor or pharmacist. They may also provide information about managing certain side effects of this drug.

Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you would like to notify the FDA about a side effect you’ve had with Xolair, you can do so through MedWatch.

Mild and serious side effects

Mild and serious side effects of Xolair are listed below. This article does not include all of Xolair’s possible side effects.

Mild side effects

Mild side effects* of Xolair may include:

Most times, mild side effects of a drug go away within a few days or a couple of weeks. Talk with your doctor or pharmacist if any side effects become severe or don’t go away.

* This is not a complete list of Xolair’s mild side effects. To learn about other mild side effects of this drug, ask your doctor or pharmacist. You can also view the drug’s prescribing information.
† To learn more about allergic reactions, see below.

Serious side effects

Serious side effects of Xolair may include:

Serious side effects from Xolair aren’t common, but they are possible. If you have serious side effects, call your doctor right away. However, if you’re having a medical emergency or your symptoms feel life threatening, call 911 or a local emergency number.

* Xolair has a boxed warning for the risk of anaphylaxis. A boxed warning alerts doctors and patients about drug effects that may be dangerous. For more information about this side effect, see the “Xolair: Precautions” section below. To learn more about allergic reactions, see below.

Allergic reaction

As with most drugs, some people can have an allergic reaction after taking Xolair. A more severe allergic reaction is rare but possible.

Xolair has a boxed warning for the risk of anaphylaxis, which is a type of severe allergic reaction. A boxed warning alerts doctors and patients about drug effects that may be dangerous. For more information about this side effect, see the “Xolair: Precautions” section below.

Possible symptoms of mild and serious allergic reactions are listed in the table below.

Mild allergic reaction symptomsSerious allergic reaction symptoms
flushing• swelling under your skin, possibly in your hands, feet, lips, or eyelids
rash• swelling in your throat or mouth
• itchingtrouble breathing

If you have an allergic reaction to Xolair, call your doctor right away. This is important because the reaction could become severe.

However, if you’re having a medical emergency or your symptoms feel life threatening, call 911 or a local emergency number.

Xolair: Uses

Prescription drugs, such as Xolair, are approved by the Food and Drug Administration (FDA) to treat certain conditions.

Using Xolair for a type of hives called chronic idiopathic urticaria (CIU)

Xolair is approved to treat a type of hives called chronic idiopathic urticaria (CIU). In this case, the drug can be used in adults and children ages 12 years and older.

With CIU, you develop hives (itchy, red bumps) on your skin that can last for weeks or months. It’s not known what causes someone to develop this condition.

Xolair can be used to treat CIU if you’ve already tried an antihistamine that didn’t work alone to treat your condition. Examples of antihistamines include loratadine (Claritin) and cetirizine (Zyrtec). In addition, Xolair may be used in combination with antihistamines to treat CIU. (See details in the “Using Xolair with other drugs” section below.)

It’s also important to note that Xolair shouldn’t be used to treat other forms of hives.

Using Xolair for nasal polyps

Xolair can be used to treat nasal polyps in adults.

Nasal polyps are benign (noncancerous) growths on the inside of your nose or sinuses. You may not notice any symptoms from nasal polyps. However, some people may experience:

  • runny nose or congestion
  • loss of taste or smell
  • headache
  • pain in the face or teeth

Xolair can be used to treat nasal polyps if certain other medications haven’t worked well enough. To treat nasal polyps, Xolair should be used in combination with other medications. This includes nasal corticosteroids, such as fluticasone (Flonase) or mometasone (Nasonex). (See more details in the “Using Xolair with other drugs” section below.)

Using Xolair for asthma

Xolair can be used to treat moderate to severe asthma in adults and children ages 6 years and older.

Asthma is a condition that affects your breathing. It may cause symptoms such as:

  • cough
  • difficulty breathing
  • wheezing
  • chest tightness

Before starting Xolair, your doctor will do a skin or blood test to check for certain allergies. If these tests are positive, your doctor may recommend Xolair. Doctors may prescribe Xolair to treat this type of asthma if certain other medications didn’t work well enough.

Typically, your doctor will recommend trying an inhaled corticosteroid, such as fluticasone (Flonase), before starting Xolair. You may also use other medications in combination with Xolair for asthma treatment. (See more details in the “Using Xolair with other drugs” section below.)

Xolair shouldn’t be used to treat a current asthma attack or other conditions related to allergies. If you’re having an asthma attack with sudden breathing symptoms, you’ll need to use a rescue inhaler. (For more details, see the “Using Xolair with other drugs” section below.)

Using Xolair with other drugs

In some cases, your doctor may recommend using Xolair in combination with other medications to treat your condition.

If you’re taking Xolair to treat CIU, your doctor may recommend taking an antihistamine medication in combination with Xolair. Examples of antihistamines include loratadine (Claritin) and fexofenadine (Allegra). They may also recommend using a topical cream, such as hydrocortisone (Cortisone).

If you’re using Xolair to treat nasal polyps, it’s recommended to take it in combination with another medication to treat your condition. Your doctor will likely recommend using a nasal spray, such as fluticasone (Flonase). They may also recommend taking an oral medication, such as montelukast (Singulair).

If you’re using Xolair to treat asthma, your doctor may also recommend a rescue inhaler to use for asthma attacks with sudden breathing problems. An example of a rescue inhaler is albuterol (Proair). (Xolair isn’t approved to treat asthma symptoms that are currently happening.)

In addition, your doctor may also recommend long-term treatments for your asthma to take in combination with Xolair. For example, they may recommend using an inhaled medication such as fluticasone (Flovent HFA) or budesonide/formoterol (Symbicort).

Using Xolair in children

Xolair is approved to treat asthma in children ages 6 years and older. The drug is also approved to treat CIU in children ages 12 years and older. (For details about these conditions, see the “Using Xolair for asthma” and “Using Xolair for a type of hives called chronic idiopathic urticaria (CIU)” sections above.)

Finding a healthcare professional for Xolair

If you would like additional information on Xolair, talk with your doctor. Use this link if you need help finding a doctor or healthcare professional. You can also use this appointment guide for asthma to help prepare for your appointment.

Xolair: Dosage

Below, you’ll find dosages that are commonly recommended for Xolair. However, you should take the dosage your doctor prescribes for you. They’ll recommend the dosage that’s best for your needs.

The dosage of Xolair that your doctor prescribes will depend on factors such as:

  • your age
  • your body weight
  • your serum IgE levels, which are measured through a blood test*
  • any health conditions you have
  • the condition you’re using Xolair to treat and the severity of the condition

* IgE is an antibody (type of immune protein). This test is used if you’re taking Xolair for nasal polyps or asthma only.

Xolair’s forms and strengths

Xolair is available as follows:

  • Forms:
    • solution in a prefilled syringe for subcutaneous injection
    • powder that’s mixed into a solution for subcutaneous injection
  • Strengths:
    • solution: 75 milligrams (mg)/0.5 milliliters (mL) and 150 mg/mL
    • powder: 150 mg

Xolair’s recommended dosages

Recommended dosages for Xolair in adults and children are described below.

Adult dosage

The recommended dosage for Xolair in adults with asthma is as follows:

  • Dose: 75 mg to 375 mg
  • Frequency: every 2 weeks or every 4 weeks

The recommended dosage for Xolair in adults with nasal polyps is as follows:

  • Dose: 75 mg to 600 mg
  • Frequency: every 2 weeks or every 4 weeks

The recommended dosage for Xolair in adults with spontaneous urticaria is as follows:

  • Dose: 150 mg or 300 mg
  • Frequency: every 4 weeks

Child dosage

The recommended dosage for Xolair in children ages 6 to 11 years with asthma is as follows:

  • Dose: 75 mg to 375 mg
  • Frequency: every 2 weeks or every 4 weeks

The recommended dosage for Xolair in children ages 12 years and older with asthma is as follows:

  • Dose: 150 mg to 375 mg
  • Frequency: every 2 weeks or every 4 weeks

The recommended dosage for Xolair in children ages 12 years and older with spontaneous urticaria is as follows:

  • Dose: 150 mg or 300 mg
  • Frequency: every 4 weeks

Dosage considerations

Below are some things to consider about Xolair’s dosage.

  • Missing a dose. If you miss a dose of Xolair, talk with your doctor to see when to take your next dose. If you go to the doctor’s office for your Xolair injections, you’ll need to reschedule your appointment. However, if you inject your dose at home, your doctor can help determine when you should take your next dose of medication. Try these medication reminder options to help avoid missing doses. You could also set an alarm, use a timer, or download a reminder app on your phone.
  • Length of treatment. Doctors typically prescribe Xolair as a long-term treatment. You’ll likely take it long term if you and your doctor feel it’s safe and effective for your condition.

Xolair: Cost

As with other medications, prices for Xolair may vary. The drug’s price will depend on factors such as:

Cost considerations for Xolair

Here are some things to consider when looking into the cost of Xolair.

Option for a 90-day supply. For some drugs, it’s possible to get a 90-day supply. If this option is approved by your insurance company, it can help lower the cost of the drug. It can also help you avoid frequent trips to your pharmacy. If you’d like to learn more about this option, ask your doctor, pharmacist, or insurance company.

Need for prior authorization. Before insurance coverage for Xolair is approved, your insurance company may require prior authorization. In this case, your doctor and insurance company will communicate about your prescription for Xolair. Then, the insurance company will decide if the drug will be covered. To find out if you need prior authorization for Xolair, contact your insurance company.

Possible cost assistance options. Financial assistance to help lower the cost of Xolair is available. The Xolair Co-pay Program or Xolair Access Solutions may help reduce its cost. To learn more and see if you’re eligible for support, call the Xolair Co-pay Program at 855-965-2472 or Xolair Access Solutions at 866-422-2377. You can also visit the manufacturer’s website for more information. Also, check out this article to learn about ways to save on prescription drugs.

Use of a mail-order pharmacy. Xolair may be dispensed through mail-order pharmacies. Getting your prescription through a mail-order pharmacy could lower its cost. It can also allow you to get the drug without leaving home. To find out more about this option, check with your doctor, pharmacist, or insurance company.

Availability of a biosimilar form. Xolair doesn’t come in a biosimilar form. Since biologic drugs are made from living cells, they can’t be replicated exactly. Biosimilar drugs are considered to be just as safe and effective as the brand-name version. Biosimilar drugs usually cost less than brand-name drugs, as well.

Xolair: Questions you may have

Here are some common questions about Xolair and brief answers to them. If you’d like to know more about these topics, ask your doctor.

Is Xolair an immunosuppressant?

No, Xolair is not considered an immunosuppressant. Immunosuppressant drugs work to treat a condition by weakening your immune system. However, Xolair isn’t believed to work in this way.

Xolair works by blocking an antibody (type of immune protein) called IgE. This substance plays a role in causing inflammation, which may cause symptoms of asthma, hives, or nasal polyps. By blocking IgE, Xolair can decrease the inflammation symptoms. (To learn more about how Xolair works, see the “Xolair: How it works” section below.)

If you have additional questions about Xolair, talk with your doctor or pharmacist.

Do doctors prescribe Xolair for allergies or eczema?

Xolair isn’t currently approved by the Food and Drug Administration (FDA) to treat allergies or eczema. The drug is currently approved to treat asthma, nasal polyps, and a type of hives called chronic idiopathic urticaria (CIU).

It’s not known if the drug may be safe or effective at treating allergies or eczema at this time. In fact, these are considered limitations of use of Xolair. (See the “Xolair: Uses” section above for details.)

However, it’s possible that your doctor may recommend using Xolair off-label to treat your allergies or eczema. Off-label use of a drug can occur if your doctor recommends using a medication for a different use than what it was approved for.

One small study shows using Xolair 2 weeks before pollen season starts may decrease the symptoms of seasonal allergies. (Symptoms of seasonal allergies may include itchy eyes, sneezing, or cough.) Another small study shows that Xolair may be effective at reducing eczema symptoms, such as rough or irritated patches of skin.

If you’re interested in learning more about using Xolair for allergies or eczema, talk with your doctor. They can help determine the best treatment plan for your condition.

Will I have withdrawal symptoms if I stop using Xolair?

No, you shouldn’t have withdrawal symptoms from stopping Xolair. (Withdrawal symptoms are side effects that can occur when you stop taking a drug that your body has become dependent on.)

Withdrawal symptoms weren’t reported in Xolair’s clinical studies. However, stopping Xolair treatment may cause the symptoms of the underlying condition to return.

It’s important that you talk with your doctor before stopping Xolair. They can recommend the best way for you to stop treatment. In addition, they may be able to recommend a different medication for your condition.

Xolair: How it works

Xolair is approved to treat asthma and a type of hives called chronic idiopathic urticaria (CIU) in adults and certain children. The drug is also approved to treat nasal polyps in adults. (To learn more about these conditions, see the “Xolair: Uses” section above.)

Xolair’s mechanism of action (how it works) is to block an antibody (type of immune protein) called IgE. This substance is responsible for causing the release of other substances, such as histamine, that can cause inflammation.

Symptoms of asthma, CIU, and nasal polyps may result from inflammation. Xolair attaches to IgE, which blocks it from releasing the other substances that cause inflammation. By blocking IgE, Xolair can decrease the symptoms of your condition.

How long does Xolair take to start working?

It may take time for you to notice that Xolair is working in your body. In fact, this medication may take months to have an effect. However, it’s important to continue taking your dosage of Xolair as your doctor instructs.

How long it takes to notice a difference in your symptoms may depend on the condition being treated and how severe it is. If you have questions about your symptoms, talk with your doctor or pharmacist.

Xolair: Alternatives

Doctors may prescribe drugs other than Xolair for your condition. Certain drugs may work better for you than others.

Xolair is used to treat hives, nasal polyps, and asthma in specific situations. Here’s a summary of other drugs that doctors sometimes prescribe for hives and asthma. 

To learn more about some alternatives to Xolair, view the following articles:

For additional information about alternatives to Xolair, ask your doctor. They can tell you about other medications available for your condition.

Xolair: How it is administered

Your doctor will recommend how you should use Xolair. It’s important to take the drug exactly as your doctor instructs.

Xolair comes as a solution and a powder. It’s given as a subcutaneous injection.

You will receive your first dose of Xolair in the hospital or at your doctor’s office. This is so that your doctor can monitor you for symptoms of an allergic reaction. (Xolair has a boxed warning about the risk of a severe allergic reaction called anaphylaxis. For details, see the “Xolair: Precautions” section below.)

Following this, it’s possible that your doctor may teach you or your caregiver to give the dose of Xolair. However, in certain situations, your doctor may recommend that you come into the office to receive each dose of Xolair. For example, if you have ever had anaphylaxis from other drugs or foods, your doctor may recommend you receive each dose in the office.

If you give yourself Xolair injections, you will use the prefilled syringe form of the drug, so you won’t have to mix it. It’s possible that you may need to use multiple syringes to get the correct dose of Xolair. If you do need to use multiple injections, you should inject them at least 1 inch apart on your skin. (See “Xolair injection sites” below for details about where to inject Xolair.)

For instructions or a step-by-step video on how to inject Xolair, see the manufacturer’s webpage. If you have additional questions about your Xolair injections, talk with your doctor or pharmacist.

Xolair injection sites

Xolair can be injected into your:

  • thigh
  • abdomen
  • outer upper arm

You shouldn’t inject Xolair within the 2 inches around your belly button. The injection of Xolair is quick and takes only about 5 to 10 seconds.

Questions about receiving Xolair

Here’s a list of common questions related to receiving Xolair.

  • When should I receive Xolair? You’ll either receive Xolair every 2 weeks or every 4 weeks. You should try to receive Xolair on the same day of the week to help keep a steady level in your body. This helps the medication work effectively. Try these medication reminder options to help avoid missing doses of Xolair. You could also set an alarm, use a timer, or download a reminder app on your phone.
  • Do I need to receive Xolair with food? No, you don’t need to take Xolair with food. Xolair is given as a subcutaneous injection. Having a full or empty stomach when taking your dose shouldn’t affect the drug.
  • Is there a best time of day to receive Xolair? Xolair isn’t used every day. It should only be received once every 2 or 4 weeks. There is no best time to take Xolair. However, you may wish to receive Xolair on the same day of the week. This can help keep a consistent amount of medication in your body.

Xolair: Consuming alcohol during treatment

There aren’t any known interactions between Xolair and alcohol.

However, it’s possible for alcohol to make some of the side effects of Xolair worse. Both Xolair and alcohol may cause symptoms such as headache, nausea, or dizziness. You may be at an increased risk of these side effects if you’re drinking alcohol during your Xolair treatment.

If you’d like to drink alcohol while you’re taking Xolair, talk with your doctor to see if it may be safe for you.

Xolair: Using while pregnant

It’s not known if Xolair is safe to use during pregnancy. A developing fetus will likely be exposed to Xolair. Clinical studies do not show an increased risk of congenital anomalies (also known as birth defects) or pregnancy loss when a pregnant person uses the drug.

However, it’s possible for Xolair to cause lower than average birth weights. It’s important to note that people using Xolair for asthma treatment may have a severe form of asthma. This condition can also cause low birth weight. As such, it’s not known if the drug or the condition itself may increase this risk.

It’s also important to note that untreated asthma during pregnancy may increase your risk of other complications. These include preeclampsia or premature birth. As such, your doctor will likely monitor asthma symptoms throughout your pregnancy to see what the best treatment options may be for you.

If you’re pregnant or planning to become pregnant, talk with your doctor before starting Xolair.

Xolair and birth control needs

It’s likely safe to take Xolair during pregnancy. However, if you’d like to learn more about your birth control options while taking Xolair, talk with your doctor. Your doctor can recommend if you should use birth control with this medication.

Xolair: Using while breastfeeding

It’s not known if Xolair may be present in breast milk or if the drug may have an effect on milk production. However, other human monoclonal antibodies are present in breastmilk. (Xolair is part of a drug class called anti-IgE antibodies, which is a form of human monoclonal antibodies.)

As such, it’s possible that a child who is breastfed may be exposed to the drug.

If you’re breastfeeding or planning to do so, talk with your doctor before starting Xolair.  

Xolair: Interactions

Xolair isn’t known to interact with other medications, supplements, or foods. However, this doesn’t mean interactions can’t occur with Xolair.

Different interactions can cause different effects. Some interactions can interfere with a drug’s effectiveness. Others can increase a drug’s side effects or cause them to be severe.

Before you start Xolair, be sure to tell your doctor about any medications, herbs, vitamins, or supplements you take. They can check for any possible interactions between these products and Xolair.

For information about drug-condition interactions, see the “Xolair: Precautions” section below.

Xolair: Precautions

This drug comes with several precautions.

FDA warning: Risk of severe allergic reaction called anaphylaxis

This drug has a boxed warning, the most serious warning from the Food and Drug Administration (FDA). A boxed warning alerts doctors and patients about drug effects that may be dangerous.

It’s possible to develop a serious allergic reaction, called anaphylaxis, from using Xolair. It’s possible for anaphylaxis to occur after just one dose of Xolair. However, it may also occur after you’ve been taking the medication for a while without issues.

Due to this risk, your doctor will recommend that you get your first dose of Xolair in their office or in a hospital. This is to see how your body may react to the drug. Most cases of anaphylaxis occur within 90 minutes to 2 hours after receiving a dose of Xolair.

Symptoms of anaphylaxis may include:

  • difficulty breathing
  • swelling of the face, lips, tongue, or throat
  • fainting
  • low blood pressure
  • rash

If you develop any symptoms of anaphylaxis during your treatment with Xolair, go to the hospital or seek emergency care right away. This can be serious and even life threatening. If you develop anaphylaxis from Xolair, your doctor will treat your allergic reaction. Then, they will recommend that you stop using Xolair and try a different medication for your condition.

Other precautions

Tell your doctor about your health history before starting treatment with Xolair. Your doctor may not recommend this medication if you have certain factors affecting your health or specific medical conditions. These situations are considered drug-condition interactions.

These factors and conditions include those listed below.

  • Bronchospasm. Xolair is a medication that can be used to prevent asthma symptoms. However, it shouldn’t be used to treat asthma symptoms that are already happening, such as bronchospasms. With bronchospasms, you may experience symptoms including sudden difficulty breathing, coughing, or dizziness. Your doctor may recommend another medication, such as albuterol (ProAir), for this use.
  • Parasitic infection. Xolair may increase your risk of developing a parasitic infection, such as roundworm. If you live in an area where parasite infections are common, you may be at an increased risk of developing an infection from using Xolair. Due to this risk, your doctor may recommend a different treatment option for you.
  • Cancer. Xolair can increase your risk of certain types of cancer, including breast cancer or prostate cancer. If you have cancer or a history of cancer, tell your doctor before starting Xolair. You may be at an increased risk of your cancer worsening or coming back while using Xolair. In this case, your doctor may monitor your cancer more often or recommend a different treatment option for you.
  • Allergic reaction. Your doctor will likely not prescribe Xolair if you’ve had an allergic reaction to it or any of its ingredients. This medication comes in a prefilled syringe, which contains a latex stopper. Therefore, if you have a latex allergy, your doctor may also recommend a different medication for you. To find out about other treatment options, talk with your doctor. Xolair has a boxed warning for the risk of anaphylaxis, which is a type of severe allergic reaction. (For more information, see the “FDA warning: Risk of severe allergic reaction called anaphylaxis” section above.)
  • Pregnancy. If you’d like additional information about taking Xolair while pregnant, view the “Xolair: Using while pregnant” section above.
  • Breastfeeding. If you’d like additional information about taking Xolair while breastfeeding, view the “Xolair: Using while breastfeeding” section above.

To learn more about the effects of Xolair that could be harmful, see the “Xolair: Side effects” section above.

Xolair: Questions for your doctor

If you have questions about Xolair, talk with your doctor. They can help advise you on whether Xolair could be a good treatment option for you.

Here’s a list of questions you may want to ask your doctor:

  • Can my dose of Xolair be lowered if I’m having side effects from the drug?
  • How can I treat side effects that I experience from Xolair?
  • If Xolair isn’t working to manage my condition, can my dose be increased?

Your doctor may also tell you about other treatment options for your condition. You may find this article helpful in learning about alternative drugs. Additionally, you can view our selection of videos on asthma.

Disclaimer: Healthgrades has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

Medical Reviewer: Heather Bruce, PharmD
Last Review Date: 2022 Aug 19
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.