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 or peripheral neuropathy
• 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 types 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 drop 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:

• diuretics: these remove fluid from the body and are used to treat conditions such as high blood pressure, heart failure and some types of kidney disease
• statins: these are used to treat people with high cholesterol levels in their blood 
• raloxifene: this is used to prevent osteoporosis (thinning of the bones) in women who have experienced the menopause
• nifedipine: this is used to treat angina and Raynaud’s phenomenon 
• nicotinic acid: this is used to treat high cholesterol

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. 

Leg cramps are a common and usually harmless condition where the muscles in your leg suddenly become tight and painful.

It usually occurs in the calf muscles, although it can affect any part of your leg, including your feet and thighs.

After the cramping has passed, you may have pain and tenderness in your leg for several hours.

Three out of four cases occur at night during sleep.

Read more about the symptoms of leg cramps.

What causes leg cramps?

Leg cramps can occur for no apparent reason, known as idiopathic leg cramps, or as a symptom or complication of a health condition, known as secondary leg cramps.

Causes of secondary leg cramps can include:

• pregnancy
• exercise 
• certain types of medication, such as statins (medicines that help lower cholesterol levels)
• liver disease

During a cramp, your muscles suddenly contract (shorten), causing pain in your leg. This is known as a spasm, and you cannot control the affected muscle.

The cramp can last from a few seconds to 10 minutes. When the spasm passes, you will be able to control the affected muscle again.

Read more about the causes of leg cramps.

When to see your GP

Speak to your GP if your leg cramps are affecting your quality of life; for example, if you have frequent leg cramps or they are interfering with your sleep.

Your GP will ask about your symptoms and examine your legs and feet. They may also ask if you have other symptoms, such as numbness or swelling, which may be a sign that you have secondary leg cramps caused by an underlying condition.

In this case, you may need further tests, such as blood tests and urine tests, to rule out other conditions.  

Treating leg cramps

Most cases of leg cramps can be relieved by exercising the affected muscles. Exercising your legs during the day will often help reduce how often you get cramping episodes.

Stretches

To stretch your calf muscles, stand with the front half of your feet on a step, with your heels hanging off the edge. Slowly lower your heels so that they are below the level of the step. Hold for a few seconds before lifting your heels back up to the starting position. Repeat a number of times.

Medication is usually only needed in the most persistent cases where cramping does not respond to exercise.

If you have secondary leg cramps, treating the underlying cause may help relieve your symptoms.

Leg cramps that occur during pregnancy should pass after the baby is born.

Treating cramps that occur as a result of serious liver disease can be more difficult. Your treatment plan may include using medications such as muscle relaxants.

Read more about treating leg cramps

Preventing leg cramps

If you often get leg cramps, regularly stretching the muscles in your lower legs may help prevent the cramps or reduce their frequency.

You might find it useful to stretch your calves before you go to bed each night (see stretching advice above or try this post-exercise calf stretch).

The following night-time advice may also help:

• If you lie on your back, make sure that your toes point upwards – placing a pillow on its side at the end of your bed, with the soles of your feet propped up against it may help keep your feet in the right position. 
• If you lie on your front, hang your feet over the end of the bed – this will keep your feet in a relaxed position and help stop the muscles in your calves from contracting and tensing.
• Keep your sheets and blankets loose.

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.

If the cause of your leg cramps is known, it may be possible to treat the underlying cause.

For example, secondary leg cramps that are related to liver disease are caused by high levels of toxins in the blood which trigger muscles spasms. Therefore, muscle relaxants can be used to help prevent your muscles from going into spasm.

If the cause of your legs cramps is unknown (primary idiopathic leg cramps), a combination of exercise and painkilling medication is usually recommended.

Exercises

Most cases of leg cramps can be treated with exercises. There are two types of exercise that you can do:

• exercises you do during an episode of cramping to relieve the pain and stop the cramping
• exercises you do during the day to reduce how often you get leg cramps

The two types of exercises are explained below. 

Exercises during cramps

During an episode of leg cramp, stretch and massage the affected muscle.

For example, if the cramp is in your calf muscle:

• Straighten your leg and lift your foot upwards, bending it at the ankle so that your toes point towards your shin.
• Walk around on your heels for a few minutes.

Exercises to prevent cramps

To reduce your risk of getting leg cramps in the future, you should do exercises to stretch the affected muscles three times a day.

For example, if your calf muscles are affected by cramps, the following exercise should be beneficial:

• stand about a metre away from a wall
• lean forward with your arms outstretched to touch the wall while keeping the soles of your feet flat on the floor
• hold this position for five seconds before releasing
• repeat the exercise for five minutes

For the best results, you should repeat this exercise three times a day, including one session just before you go to bed. Here’s an alternative calf stretch.

If you find these exercises useful you can carry on doing them for as long as you are able to.

Painkillers

If you have leg pain that persists after an episode of cramping, an over-the-counter painkiller, such as paracetamol or ibuprofen may help reduce the pain.

Quinine

Quinine was originally designed as a medication to treat malaria. Subsequent research has found that it can also be moderately effective in reducing the frequency of leg cramps.

However, there is a small chance that quinine may cause unpleasant side effects including:

• tinnitus (ringing in your ears)
• impaired hearing
• headache 
• nausea (feeling sick)
• disturbed vision
• confusion
• hot flushes

Thrombocytopenia is a rarer but more serious complication of quinine. It occurs when the number of platelets in your blood falls to a dangerously low level. Platelets help the blood to clot which means people with thrombocytopenia are at increased risk of excessive bleeding such as:

• nosebleeds 
• bleeding gums
• bleeding inside the eye
• bleeding inside the skull or digestive system (both of which can be fatal)

There have been a number of reported cases of people dying from thrombocytopenia after taking quinine to prevent leg cramps.

Never take more than your recommended dose of quinine. An overdose of quinine can result in permanent blindness and death.

Due to these small but potential risks, your GP will only prescribe quinine if there is evidence that the potential benefit of treatment outweighs the risks.

It is recommended that quinine is only prescribed when:

• you have tried the exercise techniques discussed above and they haven’t helped prevent your leg cramps
• you have frequent leg cramps which affect your quality of life

In these circumstances, you may be prescribed a four-week course of quinine. After this time, if you have not gained any benefit, the treatment will be withdrawn.

If you experience any of the side effects listed above, stop taking quinine immediately and contact your GP.