What Causes Muscle Weakness?

Medically Reviewed By Kevin Martinez, M.D.
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Muscle weakness is when you have a decrease of strength in at least one muscle. It is a common symptom of many medical conditions. This article discusses what muscle weakness is. It also talks about the causes of muscle weakness and common treatments for it.

What is muscle weakness?

Doctor checking the muscles on a person's leg
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Muscle weakness is a decrease in strength in one or more muscles. However, many people use this term to describe when they are feeling fatigued or experiencing other functional limitations, and their muscle strength is fine. Because of this, “weakness” is one of the most common reasons that people visit their doctors.

It is a common symptom of muscular, neurological, and metabolic disorders.

Depending on the specific cause, weakness may occur in one muscle, a group of muscles, or all the muscles. It sometimes co-occurs with pain, atrophy, cramping, or other types of muscular symptoms.

In some cases, muscle weakness that happens suddenly — especially on one side of the body — is a symptom of a stroke. If it occurs along with severe abdominal pain, it is sometimes a symptom of botulism. Seek immediate medical care if you or someone you are with has serious symptoms, such as:

  • a sudden change in vision
  • confusion
  • a loss of consciousness
  • severe abdominal pain
  • a severe headache
  • paralysis or an inability to move a body part

Contact your doctor if you are receiving treatment for muscle weakness and mild symptoms recur or are persistent.

What other symptoms might occur with muscle weakness?

Muscle weakness may accompany other symptoms, which vary depending on the underlying disease, disorder, or condition. Symptoms that frequently affect the muscles may also involve other body systems.

Muscular symptoms that may occur along with muscle weakness

Muscle weakness may accompany other symptoms affecting the muscles, including:

  • a burning feeling
  • frequent episodes of falling
  • a loss of muscle coordination
  • muscle spasms
  • pain
  • paralysis
  • pins and needles
  • twitching

Other symptoms that may occur along with muscle weakness

Muscle weakness may accompany symptoms that involve other body systems, including:

Serious symptoms that might indicate a life threatening condition

In some cases, muscle weakness indicates a life threatening condition, especially if it occurs suddenly and on one side of the body. This is often one of the first symptoms of a stroke.

Seek immediate medical care if you or someone you are with has any of these life threatening symptoms:

  • sudden numbness or weakness in the arms, legs, or face, especially on one side of the body
  • sudden confusion, difficulty speaking, or difficulty understanding others
  • a sudden change in vision, especially if it is only in one eye
  • sudden dizziness, difficulty walking, or loss of coordination
  • sudden severe headache with no known trigger

Every minute counts if you are experiencing a stroke. Getting prompt treatment is one of the keys to decreasing the brain damage that a stroke can cause. Knowing the symptoms is the first step in saving someone’s life if they experience a stroke.

Visit our hub to read more about bones, joints, and muscles.

What causes muscle weakness?

There are many possible causes of muscle weakness, including metabolic disorders, neurological disorders, and infections.

Metabolic causes of muscle weakness

Muscle weakness may have a metabolic cause, such as:

  • Addison’s disease: This involves a decreased production of hormones by the adrenal glands.
  • Hyperparathyroidism: This involves overactive parathyroid glands.
  • Hyperthyroidism: This condition occurs when you have an overactive thyroid.
  • Hypothyroidism: This condition occurs when you have an underactive thyroid.
  • Hypokalemia: This condition occurs when you have low potassium levels.
  • Hyponatremia: This condition occurs when you have low sodium levels.

Autoimmune causes of muscle weakness

Muscle weakness can also be due to many autoimmune conditions, including:

  • Diabetes: This is a condition wherein your body either does not make enough insulin or does not properly use the insulin it does make.
  • Graves’ disease: This is an autoimmune condition wherein your immune system attacks your thyroid.
  • Myasthenia gravis: This is a condition wherein antibodies block or alter the neurotransmitter receptors of muscle tissue.
  • Guillain-Barré syndrome: This is a rare condition wherein your body’s immune system attacks the peripheral nervous system.

Neurological causes of muscle weakness

Muscle weakness may have a neurological cause. Examples of neurological causes include:

  • Bell’s palsy: This condition involves swollen or inflamed nerves that control facial muscles.
  • Cerebral palsy: This is a group of conditions affecting brain and nervous system functions.
  • Charcot-Marie-Tooth disease: This is an inherited disorder that affects the peripheral nerves.
  • Multiple sclerosis: This is a condition that affects the brain and spinal cord, causing weakness, coordination and balance difficulties, and other issues.
  • Chronic fatigue syndrome: This is a condition that involves overwhelming fatigue that is not helped by rest.
  • Amyotrophic lateral sclerosis: Also known as Lou Gehrig’s disease, this is a severe neuromuscular disease that causes muscle weakness and disability.

Muscular disease causes of muscle weakness

Muscle weakness may also be due to a muscular disease, examples of which include:

  • Dermatomyositis: This is a condition that involves muscle inflammation and a skin rash.
  • Muscular dystrophy: This is an inherited disorder that causes a progressive loss of muscle tissue and muscle weakness.
  • Fibromyalgia: This is a condition that causes widespread chronic pain, sleep problems, and fatigue.

Infections that cause muscle weakness

Muscle weakness is sometimes due to an infection. Examples of infections that can cause muscle weakness include:

Other causes of muscle weakness

Muscle weakness may have other causes, including:

Serious or life threatening causes of muscle weakness

In some cases, muscle weakness is a symptom of a serious or life threatening condition. If you are experiencing one of these causes, contact your doctor right away or seek immediate medical care.

These conditions include:

Some studies also suggest that muscle weakness is a common symptom in those with severe COVID-19.

Read about more muscle conditions here.

What are the treatments for muscle weakness?

Treatment for muscle weakness depends on the underlying cause.

Common treatments include:

  • physical or occupational therapy
  • exercise
  • medications
  • sleep
  • a healthy diet

Summary

Muscle weakness is a common symptom of various medical conditions.

It is often mistaken for fatigue, but true muscle weakness is when there is an actual decrease in strength.

If you are experiencing muscle weakness, contact your doctor so that they can identify the underlying cause and help develop a treatment plan.

Muscle weakness can also be a symptom of something more serious, such as a stroke. If you or someone you know is experiencing symptoms of a stroke, seek immediate medical care or call the emergency services.

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Medical Reviewer: Kevin Martinez, M.D.
Last Review Date: 2022 May 30
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