Muscle weakness happens when your full effort doesn’t produce a normal muscle contraction or movement.

It’s sometimes called:

  • reduced muscle strength
  • muscular weakness
  • weak muscles

Whether you’re ill or you simply need rest, short-term muscle weakness happens to nearly everyone at some point. A tough workout, for instance, will exhaust your muscles until you’ve given them a chance to recover with rest.

If you develop persistent muscle weakness, or muscle weakness with no apparent cause or normal explanation, it may be a sign of an underlying health condition.

Voluntary muscle contractions are usually generated when your brain sends a signal through your spinal cord and nerves to a muscle.

If your brain, nervous system, muscles, or the connections between them are injured or affected by disease, your muscles may not contract normally. This can produce muscle weakness.

Many health conditions can cause muscle weakness.

Examples include:

Other conditions that may cause muscle weakness include:

Muscle weakness can also be caused by complications from certain viruses and infections, including:

Botulism, a rare and serious illness caused by Clostridium botulinum bacteria, can also lead to muscle weakness.

Prolonged use of certain drugs may also result in muscle weakness.

These drugs include:

If you experience muscle weakness for which there’s no normal explanation, make an appointment with your healthcare provider.

You’ll be asked about your muscle weakness, including how long you’ve had it and which muscles have been affected. Your healthcare provider will also ask about other symptoms and your family medical history.

Your healthcare provider may also check your:

  • reflexes
  • senses
  • muscle tone

If needed, they may order one or more tests, such as:

  • CT scans or MRI to examine the inner structures of your body
  • nerve tests to assess how well your nerves are working
  • electromyography (EMG) to test the nerve activity in your muscles
  • blood tests to check for signs of infection or other conditions

Once they’ve determined the cause of your muscle weakness, your healthcare provider will recommend appropriate treatment. Your treatment plan will depend on the underlying cause of your muscle weakness, as well as the severity of your symptoms.

Here are some of the treatment options for conditions that cause muscle weakness:

Physical therapy

Physical therapists can suggest exercises to improve your quality of life if you have conditions such as MS or ALS.

For example, a physical therapist might suggest progressive resistive exercise to help someone with MS strengthen muscles that have become weak from lack of use.

For someone with ALS, a physical therapist might recommend stretching and range of motion exercises to prevent muscle stiffness.

Occupational therapy

Occupational therapists can suggest exercises to strengthen your upper body. They can also recommend assistive devices and tools to help with day-to-day activities.

Occupational therapy can be especially helpful during the stroke rehabilitation process. Therapists can recommend exercises to address weakness in one side of your body and help with motor skills.

Medication

Over-the-counter (OTC) pain relievers, such as ibuprofen or acetaminophen, can help manage pain associated with conditions such as:

  • peripheral neuropathy
  • CFS
  • neuralgia

Thyroid hormone replacement is used to treat hypothyroidism. Standard treatment usually involves taking levothyroxine (Levoxyl, Synthroid), which is a synthetic thyroid hormone.

Dietary changes

Changing your diet can help remedy electrolyte imbalances. Your healthcare provider may also suggest taking supplements, such as calcium, magnesium oxide, or potassium oxide depending on your needs.

Surgery

Surgery may be used to treat certain conditions, such as a herniated disc or hyperthyroidism.

In some cases, muscle weakness can be a sign of something very serious, such as a stroke.

If you experience any of the following symptoms, call 911 or your local emergency services immediately:

  • sudden onset of muscle weakness
  • sudden numbness or loss of feeling
  • sudden difficulty moving your limbs, walking, standing, or sitting upright
  • sudden difficulty smiling or forming facial expressions
  • sudden confusion, difficulty speaking, or trouble understanding things
  • chest muscle weakness resulting in difficulties breathing
  • loss of consciousness