Most people have suffered the excruciatingly painful experience of a leg cramp at least once in their life, often in bed at night. A cramp is a painful spasm of the muscle, usually in the calf, but sometimes in the foot or thigh muscles. During a cramp, the affected muscle feels very hard.

Although they are extremely painful, ordinary leg cramps are more of a nuisance than anything else. Fortunately, they are not usually a sign of anything seriously wrong.

Symptoms associated with muscle cramps

Muscle cramps are a sudden, painful spasm or contraction (shortening) of a muscle. The cramp is involuntary – you have no control over the muscle spasm. Cramps often happen at night, and can wake you from sleep.

Cramps usually only last a few seconds or minutes. The affected muscle will usually look or feel as if ‘in a knot’ and may be in an unusual position (for example, your toes may be sticking up, down or to the side).

Cramps usually get better when you stretch the affected muscles. Walking around often helps relieve foot cramps. After cramps, the affected muscles may be sore and tender for a few hours. Sometimes there is even muscle swelling afterwards.

Who tends to get leg cramps?

Leg cramps (especially night cramps) seem to affect people more as they get older, usually affecting the calf muscles in the legs.

Pregnant women are also prone to cramps, especially in the second and third trimesters. Pregnancy-related cramps also usually happen at night and affect the calf muscles.

What causes cramps?

Most leg cramps have no known cause and are not serious. These cramps – sometimes called ‘true cramps’ are thought to be due to spontaneous overactivity of the nerves that supply certain muscles.

True cramps may be brought on by certain activities. Doing more exercise than usual, or prolonged or strenuous exercise, particularly in the heat (heat cramps), can bring on leg cramps. Being dehydrated can also contribute.

In some cases, cramps are a symptom of an underlying medical condition, such as:

Cramps that affect muscles other than the calf and foot muscles are more likely to have an underlying cause.

Taking certain medicines (such as some medicines used to treat high blood pressure) can also increase the likelihood of you having leg cramps. Statins (a type of cholesterol-lowering medicine) are known to be associated with side effects such as muscle soreness and weakness in some people, and may also cause leg cramps.

People having haemodialysis treatment for chronic kidney disease are also prone to having muscle cramps.

Tests and diagnosis

Your doctor will ask about your cramps, how long you have been having them and how frequently they happen. They’ll want to know what tends to bring them on or make them worse, and whether anything makes them better.

Your doctor will want to examine your legs and feet and perform a general physical examination to help rule out serious causes of cramps. They may recommend some tests to make sure the cramps are not a sign of an underlying medical condition.

Tests may include blood tests to check:

  • the levels of various salts (electrolytes) in the body, such as potassium, calcium and magnesium;
  • kidney function tests;
  • liver function tests;
  • creatinine kinase (a marker of muscle damage);
  • HbA1c test, which indicates average blood glucose levels over the last few months; and
  • thyroid hormone levels.

If the diagnosis is not clear, your doctor may refer you to a specialist for further tests and treatment.

How to treat muscle cramps

Cramps can be quickly relieved by stretching the affected muscle. When the calf is affected, this can be done by pulling your toes upwards towards you, massaging the muscle at the same time. When your feet are cramping, walking around can help stop the cramp.

You can also try applying heat (using a heat pack or by getting into a warm shower) or using a cold pack.

What can be done to prevent cramps?

Calf-stretching exercises performed several times each day and before bed may help prevent night cramps in some people. However, there is little evidence showing that stretching is effective for the prevention of cramps.

Sleeping with your legs bent and with loose covers or blankets on the bed may also help.

There are no medicines that have been proven to be safe and effective in preventing or reducing the frequency or severity of cramps. Quinine tablets were previously used to help prevent leg cramps and reduce their intensity, but are no longer recommended because they provide very little benefit and can cause serious side effects.

Magnesium supplements or vitamin B complex may help some people with leg cramps, including exercise-related cramps, but more research is needed to show that they are effective.

Treating any underlying medical conditions may also help stop muscle cramps. If your muscle cramps are thought to be a side effect from a medicine you are taking, your doctor may recommend stopping or changing your medication. Always check with your doctor before making any medication changes.

Preventing exercise-related cramps

Athletes can help prevent exercise-related cramps by ensuring they drink enough fluids in the lead up to events. Eating sufficient carbohydrates in the days before competing can also help prevent muscle fatigue and exercise-related muscle cramps.

Stretching your muscles before and after exercise may also be of benefit. Massage and rest following exercise can help too. Make sure you also drink enough fluids (a sports drink is a good choice) after exercise.

Preventing pregnancy-related cramps

Most pregnancy-related cramps happen at night, so make sure you stretch your legs before bedtime if you have been suffering from leg cramps. Making sure you are drinking enough water and other fluids during the day can also help.

Magnesium supplements or B vitamins may be helpful, although there is limited evidence. Always check with your doctor before taking any medicines, vitamins or supplements, especially during pregnancy.

When to see your doctor about leg cramps

If you’re experiencing frequent leg cramps or having cramps in other muscles, see your doctor. Also see your doctor if:

  • you are having leg cramps that are regularly disturbing your sleep;
  • your cramps are not responding to simple self-care measures;
  • you have diabetes, kidney disease or liver disease;
  • you’re concerned that the cramps may be related to medicines you are taking;
  • you have associated muscle weakness; or
  • the cramps are affecting a leg that’s swollen, red or has skin changes.