A leg cramp is an episode of sudden pain in the muscles of the leg caused by an involuntary contracting (shortening) of the leg muscle.

Most leg cramps occur in the calf muscles and, less commonly, in the feet and thighs.

Cramps can last from a few seconds up to 10 minutes. Thigh muscle cramps tend to last the longest.

During a cramping episode, the affected muscles will become tight and painful and the feet and toes will be stiff.

After the cramps have passed, you may have pain and tenderness in your legs for several hours.

When to seek medical advice

If you only get leg cramps occasionally, it is not a cause for concern and a medical diagnosis is not required.

A visit to your GP will only be necessary if you get leg cramps frequently, or if they are so painful they disrupt your sleep and you are unable to function normally the next day.

You should also visit your GP if the muscles in your legs are shrinking or becoming weaker.

When to seek immediate medical advice

There are two situations where leg cramps may be a sign of a more serious underlying health condition.

You should seek immediate medical help if:

• The cramps last longer than 10 minutes and fail to improve, despite exercise.
• Cramps develop after you come into contact with substances that could be toxic (poisonous) or infectious, for example, if you have a cut that is contaminated with soil, which can sometimes cause a bacterial infection, such as tetanus, or after being exposed to elements such as mercury or lead.

In these circumstances, contact your GP for advice immediately. If this isn't possible, contact your local out-of-hours service or call NHS 111.