Why am I so lethargic in the heat?
A doctor explains why our bodies can get exhausted in hot weather. By Abi Jackson.

Does very hot weather leave you feeling more exhausted and lethargic than usual?
There might be an initial surge of joy when the sun finally comes out ā but once temperatures really creep up, we can end up feeling physically drained, wondering whether we should follow the Mediterraneanās lead and start introducing daily siestas.
So, why does hot weather make us so tired? We asked a doctor to explainā¦
Bodies have to work harder in the heatāWhen the weather is hot, our bodies have to work harder to cool themselves down,ā says Dr Zulqarnain Shah, medical director at SSP Health and GP at SSP Health practice Colne Road Surgery.
āThe bodyās natural cooling mechanism involves increasing blood circulation near the skinās surface and promoting sweat production. These physiological changes can lead to fatigue and a feeling of lethargy. It is essential to recognise that this fatigue is a normal response to heat and is typically temporary.ā
Dehydration
Low energy and tiredness are also common when youāre lacking hydration.
āHot weather increases the rate of fluid loss through sweating, leading to dehydration. Dehydration can contribute to fatigue and make you feel even more lethargic,ā adds Dr Shah.
āTo avoid this, itās important to stay adequately hydrated by drinking plenty of fluids, especially water. Aim to drink even when youāre not feeling thirsty, as thirst is not always an accurate indicator of dehydration.ā
Heat exhaustionĀ
āProlonged exposure to heat can result in heat exhaustion, a condition characterised by symptoms such as heavy sweating, weakness, dizziness, nausea, headache, and muscle cramps. If you experience these warning signs, itās crucial to move to a cooler environment, drink fluids, and rest. If symptoms persist or worsen, seek medical attention promptly,ā says Shah.
Itās important to pay attention to warning signs, as if heat stroke develops, this is a medical emergency. Shah stresses: āHeat stroke is a severe and potentially life-threatening condition that requires immediate medical intervention. It occurs when the bodyās temperature regulation fails, and the core temperature rises dangerously high.
āSymptoms may include a high body temperature (above 39.4°C), altered mental state, confusion, rapid breathing, rapid heartbeat, and even loss of consciousness. If you suspect heat stroke, call emergency services immediately.ā
Sleep deprivation
The extra tiredness could also be linked to poor sleep, as this can really suffer in the heat.
āHot temperatures can disrupt sleep and lead to poor sleep quality. The body needs to cool down to initiate sleep, and excessive heat can make it difficult to reach the optimal sleep temperature,ā explains Shah. āTo improve sleep in hot weather, consider using fans or air conditioning, wearing lightweight and breathable sleepwear, keeping your bedroom well-ventilated, and using lighter bedding.ā
Pre-existing conditions could get worse
Many people living with chronic or long-term health conditions deal with fatigue ā which may flare up during heatwaves.
āHot weather can exacerbate symptoms and increase fatigue in individuals with certain chronic health conditions. Conditions such as heart disease, kidney problems, and respiratory issues can be particularly sensitive to heat,ā notes Shah.
āItās vital to be aware of your specific health condition and consult with your healthcare provider for personalised advice on managing your symptoms during hot weather. They may recommend staying in cooler environments, adjusting medications, or monitoring your fluid intake more closely.ā