Merck Manual

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Conditions That Cause or Contribute to Muscle Cramps

Conditions That Cause or Contribute to Muscle Cramps




Use of certain drugs

Angiotensin II receptor blockers and some beta-blockers (used to treat high blood pressure), bronchodilators (used to treat asthma), cisplatin, clofibrate, diuretics, donepezil, lovastatin, birth control pills (oral contraceptives), pyrazinamide, raloxifene, synthetic parathyroid hormone (teriparatide), tolcapone, or vincristine

Stimulants, such as amphetamines, caffeine, cocaine, ephedrine, nicotine, or pseudoephedrine

Sudden stopping of a drug

Sedatives, such as alcohol, barbiturates, or benzodiazepines

Drugs used to treat insomnia or anxiety


Electrolyte and hormonal (endocrine) disorders

Low levels of potassium (hypokalemia), low levels of magnesium (hypomagnesemia), or low levels of calcium (hypocalcemia)

Hypothyroidism (an underactive thyroid gland)

Musculoskeletal disorders

Tight calf muscles

Myopathies (disorders that affect muscle)

Structural disorders, such as flat feet or genu recurvatum (a deformity of the knee joint that causes the knee to bend backward)

Nerve disorders

Motor neuron disease (nerve disorders that affect voluntary muscles—those controlled by conscious effort)

Peripheral neuropathies (damage to nerves outside the brain and spinal cord)

Compression of a spinal nerve root

Water balance disorders

Excessive sweating with inadequate replacement of salt or potassium

Effects of dialysis—for example, if too much fluid is removed from the body or if fluid is removed too quickly

Other conditions

Exercise and lifestyle

Cramping during or soon after exercise

Sitting for a long time