What should you know about high heart rate and heat exhaustion?

In hot conditions, the body sends more blood towards the skin to release heat, while sweating removes water and salts. The heart may beat faster to maintain circulation, particularly when dehydration develops. Heat exhaustion can include excessive sweating, weakness, headache, dizziness, thirst, nausea and cool or clammy skin. Dark urine may suggest that you need more fluid, although urine colour is not a diagnosis. The risk rises with intense activity, poor acclimatisation, alcohol, some medicines and difficulty tolerating heat. Heat intolerance can also have other causes, so repeated episodes deserve review.

Stop exertion and move to a cool or shaded place. Loosen extra clothing, cool the skin with wet cloths or a fan, and lie down if light-headed. Sip cool water or an oral rehydration drink if you are awake and able to swallow; avoid forcing fluids if vomiting is persistent. Rest until symptoms and heart rate settle, and do not return to strenuous activity straight away. A clinician can advise on prevention if you have a medical condition, take regular medicines or have repeated dehydration.

Get urgent medical help if the person becomes confused, faints, has a seizure, cannot drink, keeps vomiting, develops severe weakness or does not improve promptly after cooling. Very hot skin with altered awareness may indicate heatstroke, which is an emergency. Call emergency services if chest pain, severe breathlessness or an irregular pounding heartbeat accompanies the fast rate. Do not leave a confused or collapsed person alone.

Could dehydration or heat exposure explain my heart rate? Do any medicines increase heat illness risk? How much activity is sensible while recovering? What prevention plan fits my health conditions?