Symptoms of Heatstroke
The symptoms of heatstroke are often sudden, severe, and unmistakable. They result from the body’s failure to regulate its internal temperature after prolonged heat exposure or intense physical exertion. When the core temperature exceeds 40°C (104°F), the body’s cooling systems collapse, and organs—especially the brain, heart, and kidneys—begin to suffer damage. Recognising the symptoms of heatstroke is critical, as delays in treatment can quickly lead to permanent disability or death. Rapid identification and intervention are the only effective ways to reverse this medical emergency.
A hallmark symptom of heatstroke is a very high core body temperature, typically above 40°C. This hyperthermia is the defining feature of heatstroke and causes widespread cellular damage. It often develops rapidly in exertional heatstroke (such as in athletes or labourers), or more gradually during sustained environmental exposure in vulnerable individuals. While fever is common in many conditions, the extreme temperature seen in heatstroke—alongside the context of heat exposure—is uniquely dangerous.
One of the most dangerous and urgent symptoms is altered mental status. As internal temperature rises, the brain becomes increasingly affected. Early signs may include confusion, disorientation, agitation, or bizarre behaviour. Patients may appear restless, hallucinate, or have difficulty responding to questions. As the condition worsens, more severe symptoms such as seizures, loss of consciousness, or coma may develop. These neurological symptoms indicate that the central nervous system is being compromised and require immediate medical attention.
Symptoms of Heatstroke
Another distinguishing feature is hot, dry skin, particularly in classic (non-exertional) heatstroke. The skin may feel flushed, red, and dry to the touch due to the cessation of sweating—one of the body’s main mechanisms for cooling. In contrast, patients with exertional heatstroke may still be sweating profusely, which can cause confusion during diagnosis. Regardless of skin moisture, a persistently high temperature combined with central nervous system dysfunction is always a red flag.
Rapid heart rate (tachycardia) is a common response to heat stress as the cardiovascular system attempts to cool the body and deliver oxygen to overheated tissues. The pulse may be weak or bounding, depending on hydration status and circulatory strain. This can be accompanied by low blood pressure (hypotension), particularly in patients who are dehydrated, further compromising blood flow to vital organs.
Breathing becomes fast and shallow—a condition known as tachypnoea. This may result from both fever-induced metabolic acidosis and respiratory compensation as the body tries to expel heat and manage rising carbon dioxide levels. In some cases, laboured breathing may indicate developing pulmonary complications or even coexisting respiratory illness.
Nausea and vomiting are frequent symptoms of heatstroke and can worsen dehydration. The gastrointestinal system becomes stressed during heat illness due to reduced blood flow, which impairs digestion and absorption. Abdominal cramps or discomfort may accompany these symptoms, particularly if the patient has also experienced muscle breakdown (rhabdomyolysis), which can affect electrolyte levels and gut function.
Headache
Headache is a common early symptom and can range from mild to severe. It often accompanies dizziness or a feeling of pressure in the skull, reflecting the overall strain on the central nervous system. If not addressed early, a simple headache can quickly evolve into full-blown confusion or collapse.
In many cases, muscle cramps, weakness, or stiffness are present. These symptoms arise from electrolyte imbalance—particularly involving sodium and potassium—caused by sweating and dehydration. More alarmingly, in exertional heatstroke, muscle breakdown leads to rhabdomyolysis, where damaged muscle tissue releases myoglobin into the bloodstream. This can result in dark-coloured urine, kidney damage, and generalised muscle pain.
Skin colour and appearance may vary depending on the type of heatstroke. In classic cases, the skin may appear red and dry. In exertional cases, it may be pale or mottled and damp with sweat. A bluish tint (cyanosis) in lips or fingertips may indicate oxygen deprivation and requires immediate resuscitative care.
Urinary changes are also common. Patients may stop urinating altogether (oliguria or anuria), or their urine may be dark and concentrated due to dehydration. In cases involving muscle breakdown, the urine may become tea-coloured due to the presence of myoglobin, which can damage the kidneys if not treated promptly.
Symptoms of Heatstroke
Behavioural changes may appear before other physical symptoms. Patients may become withdrawn, unusually quiet, overly irritable, or show signs of poor judgement. These subtle changes are often the first indication that something is wrong, particularly in children or older adults who may not complain of typical symptoms like headache or nausea.
In children, symptoms of heatstroke may manifest differently and include listlessness, inconsolable crying, refusal to drink, and seizures. Infants may have a sunken fontanelle (soft spot on the head), dry mouth, or fewer wet nappies. Because children have a higher surface-area-to-body-mass ratio and immature temperature regulation systems, they are more prone to rapid overheating and deterioration.
In older adults, symptoms may be more subtle and progress more slowly. They may simply appear confused, unusually tired, or unsteady on their feet. Because older individuals often have diminished thirst sensation and lower cardiac reserve, they may decompensate quickly without exhibiting dramatic symptoms. This makes vigilance in hot weather critically important for caregivers and healthcare providers.
In some cases, multi-organ failure begins before diagnosis is even made. Symptoms such as persistent hypotension, reduced urine output, altered clotting times, or elevated liver enzymes may indicate that the heart, kidneys, liver, or brain are already under severe stress. Without immediate cooling and intensive care, the likelihood of long-term damage or death increases sharply.
In summary, the symptoms of heatstroke range from high core body temperature, confusion, and dry skin to seizures, unconsciousness, and cardiovascular collapse. Recognising these symptoms—especially in individuals recently exposed to high temperatures or prolonged exertion—is the first and most important step in saving lives. Every minute counts, and early intervention dramatically improves outcomes.
