Night leg cramps happen when leg muscles suddenly tighten during sleep. They're also called nocturnal leg cramps. Night leg cramps usually involve calf muscles, although muscles in the feet or thighs might cramp as well. Stretching the tight muscle with force can relieve the pain.

Most of the time, there's no known cause for night leg cramps. In general, they're likely the result of tired muscles and nerve problems.

The risk of having night leg cramps increases with age. Pregnant people also are more likely to have night leg cramps.

Kidney failure, diabetic nerve damage and problems with blood flow are known to cause night leg cramps. But if you have one of these conditions, you probably already know. And you likely have symptoms other than just night leg cramps.

People who take medicines that increase urine output might be more likely to have night leg cramps. But it's not known if there's a direct link.

Restless legs syndrome is sometimes confused with night leg cramps. But the conditions are different. The most common symptom of restless legs syndrome is the need to move the legs when falling asleep. Restless legs syndrome is usually not painful, and the symptoms last longer than do night leg cramps.

Other health issues that can sometimes be linked to night leg cramps include:

• Acute kidney injury
• Addison's disease (adrenal insufficiency)
• Alcohol use disorder
• Anemia — a condition in which the body doesn't get oxygen due to a lack of healthy red blood cells.
• Chronic kidney disease
• Cirrhosis (scarring of the liver)
• Dehydration (when the body doesn't have enough water and other fluids to work as it should)
• Dialysis
• High blood pressure (hypertension)
• Hyperthyroidism (overactive thyroid)
• Hypoglycemia
• Hypothyroidism (underactive thyroid)
• Lack of physical activity
• Medicines, such as those used to treat blood pressure problems and high cholesterol, and birth control pills
• Muscle fatigue
• Parkinson's disease
• Peripheral artery disease (PAD)
• Peripheral neuropathy
• Pregnancy
• Spinal stenosis
• Type 1 diabetes
• Type 2 diabetes

For most people, night leg cramps are just a bother — something that jerks them awake sometimes. But some people who have them might need to see a health care provider.

Seek medical care right away if you have:

• Severe cramping that continues.
• Night leg cramps after coming into contact with a toxin, such as lead.

Schedule an office visit if you:

• Are tired during the day because leg cramps interrupt your sleep.
• Have muscle weakness and muscle wasting with leg cramps.

Self-care

To help prevent night leg cramps, try to:

• Drink plenty of fluids, but limit alcohol and caffeine.
• Stretch leg muscles or ride a stationary bicycle for a few minutes before bedtime.
• Loosen the sheets and covers at the foot of the bed.

To relieve night leg cramps, try to:

• Stretch the leg and flex the foot up toward the face.
• Massage the muscle with ice.
• Walk or shake the leg.
• Take a hot shower and point the water at the cramped muscle, or soak in a warm bath.