Heat cramps: painful muscle spasms in the heat

They often affect muscles used during activity, such as the calves, thighs, shoulders, arms or abdomen. The muscle may tighten suddenly and feel hard or difficult to move. Heat, physical effort and loss of water and salts through sweat can contribute. They can occur alongside thirst, tiredness or [Muscle Aches](/symptoms/muscle-aches/), and may be a sign that [Dehydration](/conditions/dehydration/) is developing. Heat cramps are different from an unexplained cramp that happens repeatedly in a cool setting.

Stop the activity and move to a cooler, shaded or air-conditioned place. Rest the affected muscle in a comfortable position, then gently stretch and massage it without forcing the joint. Sip water or an appropriate electrolyte drink if you are awake and able to swallow. [Oral Rehydration Therapy](/treatments/acute-and-urgent-care/oral-rehydration-therapy/) may be discussed with a clinician when fluid replacement is needed. Do not return to strenuous work until the cramp has settled and you feel recovered.

Seek urgent help if the person is confused, faints, has a seizure, cannot drink, has trouble breathing or remains very hot. Get medical advice if spasms do not improve with rest and cooling, keep returning, or occur with severe weakness, vomiting or very little urine. A clinician can distinguish heat cramps from other causes of [Muscle Cramps](/symptoms/muscle-cramps/).

Ask whether medicines, kidney or heart problems, diet, or a work pattern could affect your fluid and salt balance. Mention when the spasms began, which muscles were involved, how much you were sweating, and whether you had dizziness or dark urine.