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Leg cramps - What are leg cramps?

BMJ Group Medical Reference


Leg cramps are painful muscle contractions (spasms) that often happen at night. They're not usually serious and you might not need treatment. But if your leg cramps are troublesome and stop you sleeping, there are treatments that you can try.

We've brought together the best research about leg cramps and weighed up the evidence about how to treat them. You can use our information to talk to your doctor and decide which treatments are best for you.

People who get a leg cramp feel a sudden pain in their leg, often at night.

leg-cramp_default.jpgThis happens when a muscle or group of muscles suddenly tightens (contracts).[1] This is called a muscle spasm. Most cramps happen in calf muscles, but you can also get cramps in your thigh or in your foot.

Leg cramps usually happen at night or when you are resting. The muscle contractions can last for a few seconds or up to 10 minutes.[2] When they start, you won't know how long they'll last.[2]

What else can cause leg pain?

Cramps aren't the only cause of leg pain. You can also get severe calf pain after an injury, or if you have a Baker's cyst that bursts (a Baker's cyst is a lump of fluid that forms behind the knee).

Having a blood clot in your leg also can cause leg pain. This is known as deep vein thrombosis (DVT) and it is more serious than a leg cramp. You will need medicine to treat the clot and stop it causing serious problems. If you get swelling as well as pain in your calf or thigh, you might need an ultrasound scan to see if there's a blood clot in your leg. To learn more, see our articles on Deep vein thrombosis.

Why do I get leg cramps?

We don't know very much about what causes leg cramps or why certain people get them. Most people who have these pains in their legs are not ill. But the following things can make you more likely to get painful cramps:[1][2]

  • Being pregnant

  • Being middle-aged or older

  • Exercising

  • Not having certain salts in your body

  • Having dialysis (this is when a machine is used to clean your blood because your kidneys aren't working properly)

  • Having an imbalance of minerals in your body (this is called an electrolyte imbalance)

  • Having problems with your blood circulation or having varicose veins in your legs (varicose veins happen when valves in veins don't work properly, so blood pools in the veins)

  • Having damaged nerves or a disease that affects your nerves

  • Having a disease that affects your muscles.

Some medicines can cause leg cramps as a side effect. They include:[3]

  • Diuretics

  • Nifedipine

  • Beta-agonists

  • Steroids

  • Morphine

  • Cimetidine

  • Penicillamine

  • Statins

  • Lithium.



Your kidneys are organs that filter your blood to make urine. You have two kidneys, on either side of your body. They are underneath your ribcage, near your back.


Ultrasound is a tool doctors use to create images of the inside of your body. An ultrasound machine sends out high-frequency sound waves, which are directed at an area of your body. The waves reflect off parts of your body to create a picture. Ultrasound is often used to see a developing baby inside a woman's womb.

For more terms related to Leg cramps


For references related to Leg cramps click here.
Last Updated: June 20, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
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