Leg cramps - Causes 

Causes of leg cramps 

The cause of leg cramps is sometimes unknown (idiopathic). In other cases, there may be an underlying condition or another identifiable cause.

Idiopathic leg cramps

Although the cause of idiopathic leg cramps is unknown, there are a number of theories about what might cause idiopathic leg cramps. These include:

  • abnormal nerve activity during sleep which causes the muscle of the leg to cramp
  • excessive strain placed on leg muscles, such as when exercising, may cause the muscles to cramp at certain times
  • a sudden restriction in the blood supply to the affected muscles

Also, tendons naturally shorten over time as a person gets older, which may explain why older people are particularly affected by leg cramps. Tendons are tough bands of tissue that connect muscles to bone. If your tendons become too short, they may cause the muscles connected to them to cramp.

Secondary leg cramps

Secondary leg cramps are caused by an underlying condition or another identifiable cause. These include:

  • pregnancy: the extra weight of pregnancy can place strain on the leg muscles, making them more vulnerable to cramping
  • exercise: leg cramps are often experienced when resting after exercise
  • neurological conditions (conditions that affect the nerves in your leg muscles); for example, motor neurone disease (where the nerves in the brain and the spine gradually lose function) or peripheral neuropathy (where the nerves inside the leg are damaged)
  • liver disease: if your liver stops working properly, toxins will build up in your blood, which can make your muscles go into spasm
  • infection: some type of bacterial infection, such as tetanus, can cause muscle cramps and spasm
  • toxins: in some people, high levels of toxic (poisonous) substances in the blood, such as lead or mercury, can cause leg cramps
  • dehydration: in some people, low levels of water in the body can lead to a similar decrease in your salt levels, which can trigger muscle cramps

Medication

Certain medications have been known to cause leg cramps in a small number of people. These include:

Contact your GP if you think your medication may be causing your leg cramps as your dosage may need to be adjusted. Never stop taking a prescribed medication unless your GP or another qualified healthcare professional who is responsible for your care advises you to do so. 


Page last reviewed: 11/09/2012

Next review due: 11/09/2014

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The Yellow Card Scheme

The MHRA has produced a video that explains how the Yellow Card Scheme can be used to report the side effects of medication