A fever is an elevation of the body’s core temperature above its normal range, typically exceeding 100.4°F (38°C). It often signals the body’s physiological response to an infection, inflammation, or another illness. Blood pressure, conversely, is the force exerted by circulating blood against the walls of the arteries. This measurement includes two numbers: systolic pressure, recorded when the heart beats, and diastolic pressure, measured when the heart rests between beats.
Fever’s Immediate Impact on Blood Pressure
A fever often leads to a temporary increase in heart rate and a slight elevation in blood pressure. This occurs as the body combats infection and regulates temperature. The increased heart rate helps circulate blood more efficiently to support the immune response. For healthy individuals, this fluctuation is often a compensatory mechanism and not a cause for immediate concern.
The Body’s Response to Fever
When a fever develops, the body’s metabolic rate increases to generate heat, helping fight pathogens. This heightened activity leads to a faster heart rate to meet the body’s increased demand for oxygen and nutrients. This increased cardiac output contributes to changes in blood pressure.
The body also attempts to dissipate excess heat through vasodilation, the widening of blood vessels. This can cause a decrease in peripheral resistance, potentially leading to a drop in blood pressure. However, increased heart rate and cardiac output often compensate, resulting in a slight increase in systolic pressure. Fever can also lead to dehydration due to increased sweating and fluid loss, which reduces blood volume. While dehydration can cause blood pressure to drop, the body may then overcorrect by constricting blood vessels and raising blood pressure.
When to Monitor and Seek Medical Advice
Monitoring blood pressure during a fever is important for individuals with pre-existing conditions like hypertension. While a modest elevation is common, a significant or sustained increase or drop in blood pressure warrants medical attention. For instance, a reading of 180/120 mmHg or higher, accompanied by symptoms like chest pain or severe headache, requires immediate medical evaluation.
Conversely, a significant drop in blood pressure can signal severe infection and may lead to symptoms like dizziness, fainting, or confusion. If a fever is accompanied by symptoms like severe headache, rash, stiff neck, mental confusion, persistent vomiting, difficulty breathing, or chest pain, seek immediate medical attention. Staying well-hydrated by drinking plenty of fluids is also important to manage fever and help maintain stable blood pressure.