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Muscle weakness in arms or legs

Also called: Weak arms or legs, lack of strength

Muscle weakness means your muscles have less strength than usual. Feeling weak all over is common with illnesses like the flu. Sudden weakness in one arm, leg, or side of the body can be a sign of a stroke and is an emergency.

Feeling weakOften from an illness like the flu
True weaknessA real loss of strength a doctor can measure
Emergency signSudden weakness in one arm, leg, or side
If you think it's an emergency, call 911.Thinking about suicide? Call or text 988.

Overview

Weakness can affect your whole body or just one area. Weakness in one area is easier to notice and is more likely to come from a problem with nerves or muscles.

Sometimes you feel weak but your strength is actually normal. This often happens with infections like the flu. Other times there's a real loss of strength that a doctor can find on an exam.

When to get medical care

Call 911Sudden weakness or numbness in the face, arm, or leg, especially on one side. Sudden trouble speaking, seeing, or walking. These can be signs of a stroke. Weakness with trouble breathing or swallowing.
Get care todaySudden weakness after a viral illness. Weakness that is quickly getting worse. Weakness in one area of the body.
See a doctor soonWeakness that doesn't go away and has no clear cause.

Causes

Weakness can come from problems with the brain and nerves (like a stroke, multiple sclerosis, a pinched nerve, Bell palsy, or Guillain-Barré syndrome), muscle diseases, low sodium or potassium, thyroid problems, anemia, myasthenia gravis, or poisoning (like botulism). Infections like the flu can make you feel weak all over.

OwieClear has pages on 3 conditions that can cause muscle weakness in arms or legs. Each shows how soon to get care.

Common causes

  • Charcot-Marie-Tooth diseaseSee a doctor if it doesn't get better

    An inherited nerve disease causing weakness and numbness that starts in the feet and lower legs, with high arches, curled toes, foot drop, frequent tripping,…

  • Inflamed muscles (dermatomyositis or polymyositis)See a doctor if it doesn't get better

    Autoimmune conditions that inflame the muscles, causing weakness in the shoulders, hips, and thighs (trouble climbing stairs or lifting arms).

Less likely causes

  • Vitamin D deficiencySee a doctor if it doesn't get better

    Low vitamin D, often from little sun, darker skin, or certain health problems.

What you can do at home

  • Follow your doctor's treatment for the cause of the weakness.
  • Don't wait out sudden weakness. Sudden weakness on one side needs emergency care right away.
  • Prevent falls. Use a cane or walker if you're unsteady, and clear clutter from walkways.

At the doctor

The doctor will try to find what's causing the weakness. Treatment depends on the cause.

Questions you may be asked

  • When the weakness started and whether it came on suddenly
  • Whether it's in one area or all over
  • Whether it comes and goes or is always there
  • Recent illnesses or injuries
  • Medicines you take, and other symptoms like numbness or tingling

The exam

The doctor will check your heart, lungs, and thyroid, and test the strength and reflexes of your muscles and nerves.

Tests

  • Blood and urine tests
  • X-rays, ultrasound, or an MRI
  • Nerve and muscle tests

Check your symptoms

Most symptoms have more than one possible cause. The symptom checker looks at all of your symptoms together, plus your age, and shows how soon to get care.

Start the symptom checker

Sources

Last updated 2026-11-13.