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. Read on to learn more about muscle spasms and how to treat and prevent them.

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

  • Taking certain medications, such as diuretics or water pills

  • Certain medical conditions, such as kidney failure or diabetes

  • Being pregnant

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 health care provider about steps to take to avoid muscle spasms. These may include:

  • Drinking enough fluids to avoid dehydration, especially when you exercise.

  • Taking vitamin or mineral supplements.

  • Getting regular exercise.

  • Stretching regularly, especially before exercise.

  • Limit caffeine and smoking.

  • Taking 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

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