Muscle Spasm

A muscle spasm (also called a cramp) is an involuntary muscle contraction. The muscle tightens quickly and strongly. A hard lump may form in the muscle. Muscle spasms are very painful. Here's how to treat and prevent muscle spasms.

Outline of right lower leg showing calf muscles contracting in a spasm.

What causes muscles to spasm?

Often, the cause of a muscle spasm is not known. Muscle spasm is due to irritation of muscle fibers. Some things can make a muscle spasm more likely. These include:

  • Injury

  • Heavy exercise

  • Overtired muscles

  • A muscle held in one position for a long time

  • Dehydration

  • Low levels of certain minerals in the body

  • Certain medicines, such as diuretics or water pills

  • Certain medical conditions, such as kidney failure or diabetes

  • Pregnancy

Stopping a muscle spasm

Muscle spasms often come and go quickly. When a muscle goes into spasm, very gently stretch and massage the muscle. This may help calm the muscle fibers. Then rest the muscle.

Preventing muscle spasms

Although there is little or no evidence that staying hydrated, taking certain vitamins or minerals, or stretching works to prevent cramps, these measures may help and have other benefits. Talk to your healthcare provider about steps to take to prevent muscle spasms. Try to:

  • Drink enough fluids to prevent dehydration, especially when you exercise.

  • Take vitamin or mineral supplements.

  • Get regular exercise.

  • Stretch regularly, especially before exercise.

  • Limit caffeine and smoking.

  • Take a prescription muscle relaxant.

When to call your doctor

Call your doctor if you have any of the following:

  • Severe cramping

  • Cramping that lasts a long time, does not go away with stretching, or keeps coming back

  • Pain, tingling, or weakness in the arms or legs

  • Pain that wakes you up at night