Muscle cramps and spasms: causes, red flags and what helps

The NHS describes a leg cramp as a muscle in the leg tightening and causing a sudden pain that can make it hard to move. After it passes the muscle may be tender. Spasm is a similar word for an involuntary tightening, and some people use it to describe a fleeting twitch rather than a sustained cramp.

Cramp needs distinguishing from other leg complaints that mimic it. The NHS restless legs page says conditions that can cause similar symptoms include leg cramps and peripheral neuropathy, while NICE CKS lists nocturnal leg cramps, peripheral neuropathy, akathisia and intermittent claudication in the differential of restless legs. The practical difference is that in restless legs there is an urge to move the legs with uncomfortable sensations, worse in the evening and eased by movement, whereas in a cramp the muscle is hard and painful.

Many cramps have no identifiable cause. The NHS says the reason for some is unknown. Where there is a cause, the commonest are listed below.

The NHS says to see a GP if leg cramps are disturbing your sleep, if you also have numbness or swelling in your legs, or if cramps last longer than 10 minutes. The combination of swelling in one leg with pain, redness and heat is a different problem: the NHS says a blood clot in the leg can cause pain, redness and swelling in one leg, usually the calf, and can lead to a pulmonary embolism, for which sudden breathing difficulty, chest pain and coughing blood are warnings that need urgent help.

Two further points are worth raising with a GP: cramps that began soon after starting a new medicine, since the NHS lists statins and diuretics among possible causes, and any muscle weakness, which is not typical of simple cramp.

• Cramps lasting longer than 10 minutes, or happening most nights and disturbing sleep.

• Numbness or swelling in the legs.

• One calf that is swollen, red, hot and painful, particularly after travel or immobility.

• Weakness or muscle wasting.

• Cramps beginning soon after a new medicine.

• Sudden breathlessness, chest pain or coughing blood, which are emergencies.

The NHS says a GP will examine you to find the reason for your leg cramps and suggest treatment depending on the cause. Typical questions: when the cramps occur, how long they last, which muscles, how often, whether the legs feel restless, numb or swollen, what you drink and eat, alcohol intake, exercise, pregnancy, and every medicine you take, including statins and water tablets.

Examination includes the legs for swelling, circulation and tenderness, muscle strength and sensation. Blood tests for kidney function, salts, thyroid and ferritin are considered when the history points to a cause, as CKS suggests for restless legs, where serum ferritin checks for iron deficiency.

During a cramp the NHS suggests stretching and massaging the muscle, and standing up and putting weight on the cramping leg, although most cramps go away without anything being done. Paracetamol or ibuprofen can ease soreness afterwards but they take too long to help while the cramp is happening.

To prevent them the NHS recommends regular calf-stretching exercises: stand facing a wall at arm's length with feet flat, lean forward pressing the hands against the wall until the calves stretch, hold for 2 or 3 seconds, and repeat for about 5 minutes, 3 times a day, with the last session just before bed. If cramps reduce, once or twice a day may be enough. Staying well hydrated and checking whether a medicine is contributing are sensible additions; the NHS says to speak to your GP before stopping a prescribed medicine.

The NHS says treatment from a GP depends on the cause. It may be stretching exercises, or quinine tablets if exercise has not helped. Quinine is not suitable for everyone, and the GP will discuss potential risks and side effects. Treating an underlying cause, such as dehydration, a medicine side effect or iron deficiency, can resolve the cramps.

If the pattern is restless legs rather than cramp, the NHS suggests daytime exercise, regular sleep times, a warm bath or heat pads, walking and stretching during symptoms, avoiding caffeine after midday and alcohol for at least 2 hours before bed. CKS adds that iron supplementation is recommended where ferritin or transferrin saturation is low.

A GP is the right contact when cramps are frequent, long-lasting, disturb sleep or come with other symptoms. A pharmacist can advise on painkillers for soreness. In pregnancy, midwives can advise on cramps, which the NHS lists as common in later stages.