Side Effects of Fosamax: What to Know

Medically Reviewed By Damilola Omopariola, PharmD, BCACP

Fosamax: Introduction

Fosamax is a brand-name prescription drug. It’s a type of drug called a bisphosphonate and contains the active drug alendronate. It comes as a tablet and is taken by mouth.

Fosamax is approved by the Food and Drug Administration (FDA) to:

Similar to other drugs, Fosamax may cause side effects. Read below for information about possible side effects, including common, mild, and serious ones.


Fosamax is typically taken for several years when used to treat or prevent osteoporosis. For treating Paget’s disease, it’s typically taken for 6 months. For a general overview of Fosamax, including details about its uses, see this article.

If you’d like to take Fosamax, search here to find a healthcare professional who might prescribe it.

* Sex and gender exist on spectrums. In this article, use of the term “female” refers to sex assigned at birth.

Fosamax: More common side effects

Some of Fosamax’s side effects may be more common than others. These side effects may last only a few days to weeks. However, some side effects may last longer or become severe or bothersome. Tell your doctor or pharmacist if you have concerns about any side effects with Fosamax.

In Fosamax’s clinical studies, these were some side effects that occurred more often:

Fosamax: Mild side effects

Fosamax can cause mild side effects, which are listed below. However, this list doesn’t include all possible mild side effects. To learn more about Fosamax’s side effects, view the drug’s prescribing information.

Fosamax’s mild side effects include:

The side effects listed above may last only a few days to weeks. However, some side effects may last longer or become severe or bothersome. Tell your doctor or pharmacist if you have concerns about side effects with Fosamax.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Fosamax and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Fosamax: Side effects explained” below.
† This side effect wasn’t reported in clinical studies of Fosamax, but has occurred since the drug was approved for use. For more information, see “Fosamax: Side effects explained” below.

Fosamax: Serious side effects

It’s possible to have serious side effects with Fosamax. Serious side effects are listed below, but this list may not include all possibilities. To learn more about Fosamax’s side effects, view the drug’s prescribing information.

Call your doctor right away if you have serious side effects with Fosamax. However, if you think you’re having a medical emergency or have life threatening side effects, call 911 or your local emergency number.

Serious side effects of Fosamax and their possible symptoms include:

* For more information about this side effect, see “Fosamax: Side effects explained” below.
† An allergic reaction is possible after taking Fosamax. This side effect was not reported in clinical studies, but has happened since the drug was approved for use. For more information about allergic reactions, see “Fosamax: Side effects explained” below.

Fosamax: Common questions about side effects

Here are some common questions about the drug’s side effects and answers to them. Talk with your doctor if you have other questions about this drug.

Are Fosamax side effects different for older people?

No, Fosamax side effects aren’t expected to be different for older adults.

In clinical studies, there were no differences in side effects between people ages 65 years or older and younger people.

However, it is possible for side effects of a drug to be different in older adults. This is because older people are more likely to have additional medical conditions or take other medications. These factors may increase the risk of side effects from Fosamax or other medications.

If you have questions about side effects of Fosamax, including whether your age affects your risk, talk with your doctor or pharmacist.

Does Fosamax cause weight gain?

No, Fosamax isn’t expected to cause weight gain. This wasn’t reported as a side effect in clinical studies.

Fosamax belongs to a drug class called bisphosphonates. These medications are commonly prescribed to treat or prevent osteoporosis. Older adults are more likely to be affected by osteoporosis. As people age, they also begin losing body weight and bone mass. A 2018 study found that bisphosphonates, such as Fosamax, can help prevent age-related loss of body weight.

So Fosamax isn’t known to cause weight gain. However, it may help prevent weight loss that’s related to aging.

Talk with your doctor if you’re concerned about your weight. Your doctor can help you develop a plan to address your concerns.

What are the long-term side effects of Fosamax?

Fosamax may cause long-term side effects. These are side effects that may continue for a long time, possibly after you stop taking Fosamax. They may also start after you’ve taken Fosamax for a long time or after you stop taking it.

Long-term side effects of Fosamax include:

Talk with your doctor or pharmacist if you have questions about long-term side effects of Fosamax.

* To learn more about these side effects, see the “Fosamax: Side effects explained” section below.

Does Fosamax have an effect on blood pressure?

Not typically. In clinical studies of Fosamax, high and low blood pressure were not reported as side effects.

However, Fosamax can rarely cause hypocalcemia (low blood calcium level). In extreme cases, this can cause low blood pressure. Hypocalcemia can also happen if you take too much Fosamax.

It’s also important to keep in mind that Fosamax is often used with calcium and vitamin D supplements. Taking too much calcium can cause hypercalcemia (high blood calcium level), which may cause high blood pressure.

Talk with your doctor or pharmacist if you have additional concerns about Fosamax and blood pressure.

Fosamax: Side effects explained

Here’s detailed information about some of Fosamax’s side effects.

Damage to the jaw

Damage to the jaw wasn’t reported in clinical studies of Fosamax. However, it has happened in rare cases since Fosamax was approved for use. Also, damage to the jaw is a known side effect of bisphosphonate medications. (And Fosamax is a bisphosphonate.)

Specifically, bisphosphonates such as Fosamax can cause jaw necrosis (bone loss in the jaw). This side effect can happen at any time while you’re taking Fosamax. However, your risk of damage to the jaw may increase over time during treatment with Fosamax.

Symptoms of jaw necrosis can include loose teeth, jaw numbness, and pain or skin discoloration around your jaw. In extreme cases, the jawbone may be exposed on the inside of your mouth.

Risk factors of jaw necrosis include:

  • having invasive dental procedures, such as tooth extraction
  • having certain other conditions, including:
  • taking certain other medications, including:
  • difficulty maintaining oral hygiene
  • using dentures that do not fit

What to do

Before you begin taking Fosamax, your doctor will examine your mouth. They may refer you to see your dentist before prescribing Fosamax to you.

To help prevent damage to the jaw while you’re taking Fosamax, it’s important to practice good oral hygiene. This includes regularly brushing and flossing your teeth.

If you develop jaw necrosis from taking Fosamax, you’ll likely need care from a dental surgeon. Your doctor may also have you permanently stop taking Fosamax.

If you have a planned dental procedure while taking Fosamax, talk with your doctor. They may recommend pausing your treatment with Fosamax to reduce your risk of jaw damage.

Effects on teeth

It’s possible to have teeth-related side effects with Fosamax. Bisphosphonates, such as Fosamax, can cause jaw necrosis (bone loss in the jaw). And jaw necrosis can lead to effects on teeth.

Dental side effects caused by damage to the jaw may include loose teeth.

Additional symptoms and information about jaw necrosis are described in “Damage to the jaw” directly above.

What to do

Your doctor will examine your mouth before you begin taking Fosamax. They may refer you to see your dentist before prescribing Fosamax to you. To help prevent damage to your jaw and effects on your teeth while taking Fosamax, it’s important to practice good oral hygiene. This includes regularly brushing and flossing your teeth.

If you develop dental side effects due to jaw necrosis from taking Fosamax, you’ll likely need care from a dental surgeon. Your doctor may also have you permanently stop taking Fosamax.

Hair loss

Hair loss wasn’t reported as a side effect in clinical studies of Fosamax. However, it has happened since the drug was approved for use.

It’s also possible that other medications you take may cause hair loss. For example, hair loss can be caused by estrogen replacement therapy, which may be used to treat symptoms of menopause. (Fosamax is prescribed to treat or prevent osteoporosis in postmenopausal females.)*

A drug class called glucocorticoids may also cause hair loss. (Fosamax is prescribed to treat osteoporosis caused by glucocorticoids.)

What to do

Talk with your doctor if you have hair loss while taking Fosamax. They can evaluate your symptoms to determine possible causes. If your doctor thinks your hair loss is a side effect of Fosamax, they may recommend you stop taking the medication. They may also recommend a treatment for your hair loss.

* Sex and gender exist on spectrums. In this article, use of the term “female” refers to sex assigned at birth.

Bone, joint, or muscle pain

Bone, joint, and muscle pain are known side effects of bisphosphonate medications, including Fosamax.

In clinical studies, people reporting bone, joint, or muscle pain had mild pain symptoms. However, since the drug was approved for use, there have been rare cases of severe bone, joint, or muscle pain.

Symptoms of bone, joint, or muscle pain were reported as early as 1 day after people started taking Fosamax. However, these symptoms also occurred in people who had taken Fosamax for months.

In clinical studies of Fosamax, bone, joint, or muscle pain was more likely to occur in postmenopausal females.*

What to do

Talk with your doctor if you have mild bone, joint, or muscle pain. They may recommend using over-the-counter pain relievers such as ibuprofen (Advil) or acetaminophen (Tylenol). Do not take these medications unless your doctor or pharmacist tells you it’s safe to do so. An ice pack may also ease mild bone, joint, or muscle pain.

If your bone, joint, or muscle pain is severe or doesn’t go away, your doctor will likely have you stop treatment with Fosamax. For most people, stopping Fosamax relieves symptoms of bone, joint, or muscle pain.

* Sex and gender exist on spectrums. In this article, use of the term “female” refers to sex assigned at birth.

Effects on the esophagus

Similar to all bisphosphonates, Fosamax can have effects on the esophagus. (The esophagus is the tube that connects your mouth to your stomach.) These effects weren’t common in the drug’s clinical studies, but they can occur and may rarely be serious.

Specifically, bisphosphonates such as Fosamax can cause:

  • esophagitis (inflammation in your esophagus)
  • ulcers in your esophagus, which may cause bleeding
  • erosion of your esophagus
  • holes in your esophagus or a narrowing of your esophagus, in rare cases

Symptoms of these effects can include difficulty or pain with swallowing. They may also include a hoarse voice, heartburn, or chest pain.

In rare situations, effects on the esophagus caused by Fosamax can be severe and require treatment in a hospital.

What to do

There are some steps you can take to help prevent Fosamax from affecting your esophagus. These are listed in the table below.

Things to do Things to avoid
• Take your Fosamax dose as soon as you wake up, before you eat, drink, or take other medications. • Do not eat, drink (except plain water), or take other medications for at least 30 minutes after taking your Fosamax dose.
• Take Fosamax tablets while sitting or standing. • Do not lie down for at least 30 minutes after taking your Fosamax dose and until you have eaten something.
• Swallow Fosamax tablets whole with a full glass (6 to 8 ounces) of plain water. • Do not chew or suck on Fosamax tablets.

It’s very important that you take Fosamax exactly as your doctor instructs. If you notice symptoms of esophagus problems while taking Fosamax, stop taking the medication and tell your doctor right away.

Your doctor can evaluate your symptoms and determine whether you should continue treatment or stop taking Fosamax.

Allergic reaction

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

Allergic reactions weren’t reported in clinical studies of Fosamax. However, they have happened since the drug was approved for use.

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

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

If you have an allergic reaction to Fosamax, call your doctor right away. This is important to do 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.

Fosamax: Precautions

Be sure to talk with your doctor about your health history before you take Fosamax. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health.

The conditions and factors to consider include those described below.

Fosamax precautions

Precautions to consider before taking Fosamax include:

Digestive problems, including problems swallowing. Be sure to tell your doctor if you have digestive problems before taking Fosamax. This includes problems swallowing and malabsorption syndrome (trouble absorbing minerals). Fosamax can cause digestive side effects such as esophagitis or ulcers in your esophagus. Having existing digestive problems can raise your risk of these side effects, including the risk of severe effects. Your doctor can determine whether Fosamax is safe for you to take.

Low blood calcium level. Hypocalcemia (low blood calcium level) must be treated before you begin treatment with Fosamax. It’s possible for Fosamax to lower your blood calcium. If you have existing low blood calcium, taking Fosamax may make your condition worse. It may even cause you to have severe hypocalcemia, which may cause low blood pressure and other heart problems. Your doctor can discuss treatment options for low blood calcium with you before you start taking Fosamax.

Kidney problems. Fosamax is likely safe to take if you have mild or moderate kidney problems. However, taking Fosamax isn’t recommended if you have severe kidney problems such as severe chronic kidney disease. This is because your body relies on your kidneys to get rid of Fosamax after you take a dose. So if your kidneys are not working correctly, this can increase your risk of side effects from Fosamax. Your doctor can determine whether Fosamax is safe to take with your kidney problems.

Allergic reaction. If you’ve had an allergic reaction to Fosamax or any of its ingredients, your doctor will likely not prescribe Fosamax. Ask your doctor what other medications may be better options for you.

Consuming alcohol during Fosamax treatment

There isn’t a known interaction between alcohol and Fosamax.

However, a 2019 study found that consuming alcohol is a risk factor of osteoporosis, which Fosamax is used to prevent and treat.

Consuming alcohol may also raise your risk of certain side effects with Fosamax. Examples include:

If you consume alcohol, talk with your doctor about how much, if any, is safe for you to drink while taking Fosamax.

Pregnancy and breastfeeding during Fosamax treatment

It’s not known whether it’s safe to take Fosamax during pregnancy. The drug’s manufacturer recommends stopping Fosamax if you become pregnant while taking the drug. If you are pregnant or planning a pregnancy, talk with your doctor before you start taking Fosamax.

It also isn’t known if it’s safe to breastfeed while taking Fosamax. It’s not known whether the drug is present in breast milk or whether it could cause side effects in a child who is breastfed. Talk with your doctor about healthy ways to feed your child while taking Fosamax.

Fosamax: What to discuss with your doctor

Talk with your doctor or pharmacist to find out more information about Fosamax. If you have questions about the drug’s side effects, your pharmacist or healthcare professional can help answer them for you.

In addition to discussing Fosamax with your doctor, you may find the following articles helpful in learning more.

  • Overview of Fosamax. To read an overview of Fosamax, see this article.
  • Drug comparison. To learn how Fosamax compares with Prolia, read this information. To learn how Fosamax compares to Boniva, explore this information
  • Details about osteoporosis. To learn more about osteoporosis, which Fosamax is used to treat, see this article.

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: Damilola Omopariola, PharmD, BCACP
Last Review Date: 2022 May 7
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