Heat exhaustion symptoms may be unpleasant for the sufferer and can come on suddenly.
Caused by high temperatures, Britons may be particularly at risk during this summers heatwave.
The condition is “not serious”, according to the NHS, but can lead to some uncomfortable symptoms.
“It usually gets better when you cool down,” they continued online.
Sufferers need to be careful to avoid their condition turning into heat stroke, which can be life threatening.
Signs of heat exhaustion include a headache, dizziness and confusion, and loss of appetite, according to the NHS.
Feeling sick, excessive sweating and pale, clammy skin, and muscle cramps may also be a sign.
Fast breathing, a temperature above 38C or intense thirst can also be a symptom of heat exhaustion.
“Symptoms are often the same in adults and children, although children may become floppy and sleepy,” they continued.
“If someone is showing signs of heat exhaustion they need to be cooled down,” the healthcare provider advised.
The Mayo Clinic said heat exhaustion symptoms can include “heavy sweating and a rapid pulse, a result of your body overheating.
“It’s one of three heat-related syndromes, with heat cramps being the mildest and heatstroke being the most severe.”
The condition may be caused by high temperatures, “particularly when combined with high humidity”, and strenuous physical activity.
Describing how it comes about, the Mayo Clinic said in hot weather “your body cools itself mainly by sweating. The evaporation of your sweat regulates your body temperature.
“However, when you exercise strenuously or otherwise overexert in hot, humid weather, your body is less able to cool itself efficiently.
“As a result, your body may develop heat cramps, the mildest form of heat-related illnesses.”
It is possible to avoid heat exhaustion by taking steps to keep cool.
“Drink plenty of cold drinks, take cool baths or showers and wear light-coloured loose clothing,” advised the NHS.
“Sprinkle water over skin, avoid the sun between 11am and 3pm, avoid excess alcohol and extreme exercise,” they continued.
“There is a high risk of heat exhaustion or heat stroke during hot weather or exercise”, they warned.
For someone receiving cooling treatment, their temperature should start to drop “within 30 minutes”.