Fever can raise your blood pressure temporarily, but it usually returns to normal once the fever breaks

When you have a fever, your body's temperature climbs as part of fighting an infection or illness. During this time, your blood pressure often rises too — sometimes noticeably. This happens because fever makes your heart work harder and causes your blood vessels to constrict. The increase is usually temporary and goes away once your body temperature returns to normal and the underlying illness resolves.

The relationship between fever and blood pressure is straightforward: the higher your fever, the more your blood pressure is likely to spike. Someone with a 103°F fever will typically see a larger blood pressure jump than someone with a 100°F fever. This is a normal physiological response, not a sign that you have developed high blood pressure as a condition.

Key Takeaways

  • Fever raises blood pressure temporarily because your heart works harder and blood vessels narrow as your body fights infection.
  • Blood pressure returns to its baseline once your fever breaks and the underlying illness resolves, so the spike is not permanent.
  • If you have existing high blood pressure, a fever can push your readings higher than usual, which is why monitoring matters during illness.
  • Treating the fever with over-the-counter medications like acetaminophen or ibuprofen can help lower both temperature and blood pressure.
  • Contact a doctor if your blood pressure stays elevated after your fever is gone, or if you have chest pain, shortness of breath, or severe headache during fever.

Why fever raises blood pressure in the first place

Your body raises its temperature deliberately when fighting infection. To maintain that higher set point, your nervous system tells your heart to pump faster and your blood vessels to tighten. Both of these changes increase blood pressure. Additionally, fever causes your body to release stress hormones like adrenaline and noradrenaline, which further constrict blood vessels and speed up your heart rate.

This is not a malfunction — it is your body's defense mechanism at work. The elevated blood pressure helps deliver immune cells and antibodies to infected areas more efficiently. Once the infection clears and your body temperature drops back down, these changes reverse and blood pressure normalizes.

How much your blood pressure typically rises during fever

The amount of blood pressure increase varies from person to person and depends on how high the fever climbs. A general rule is that blood pressure rises roughly 1 to 2 millimeters of mercury (mmHg) for every 1 degree Fahrenheit increase in body temperature. So a 2-degree fever might raise your systolic pressure (the top number) by 2 to 4 mmHg, while a 4-degree fever could raise it by 4 to 8 mmHg.

For someone with normal blood pressure, this temporary increase is usually not concerning. For someone who already has high blood pressure, the same fever can push readings into a range that feels uncomfortable or worrying. This is why people with existing hypertension should monitor their blood pressure during illness and stay in touch with their doctor if the fever is significant or prolonged.

When fever-related blood pressure spikes are a concern

A temporary blood pressure rise from fever alone is not dangerous in most cases. However, you should contact a doctor if any of these occur during or shortly after a fever: chest pain or pressure, shortness of breath, severe headache, confusion, vision changes, or blood pressure that remains elevated even after the fever is completely gone.

These symptoms can signal that something more serious is happening — such as a severe infection, heart involvement, or a stroke-related condition — rather than a simple fever response. Do not assume the elevated blood pressure will resolve on its own if these warning signs are present.

Managing blood pressure during fever

Treating the fever itself is the most direct way to bring blood pressure back down. Over-the-counter fever reducers like acetaminophen or ibuprofen lower body temperature and, as a result, reduce the blood pressure spike. Follow the dosing instructions on the package or as directed by your doctor.

Beyond medication, rest, hydration, and cool compresses can help your body recover faster. Staying hydrated is particularly important because dehydration during fever can make blood pressure fluctuations worse. Avoid caffeine and salt during acute illness, as both can add to blood pressure elevation.

What happens after the fever breaks

Once your fever is gone and the infection is cleared, your blood pressure should return to whatever your baseline is within hours to a day. If you have a history of high blood pressure, your readings should go back to their usual pattern. If your blood pressure remains elevated a week or more after the fever is completely resolved, that is a signal to see your doctor — it may indicate the infection is not fully cleared, or there could be another issue at play.

Keep a simple record if you are monitoring at home: write down your temperature, blood pressure reading, and the time. This information helps your doctor understand what happened and whether the pattern was normal for you or unusual.

Fever versus chronic high blood pressure

It is important not to confuse a temporary blood pressure rise from fever with a diagnosis of high blood pressure. High blood pressure is diagnosed when readings are elevated on multiple occasions over time, not during acute illness. A single elevated reading during fever does not mean you have hypertension.

However, if you notice that your blood pressure is elevated even when you are not sick, or if it stays high weeks after an illness, that is worth discussing with your doctor. Some infections can trigger lasting changes in blood pressure regulation, though this is uncommon. Your doctor can determine whether the elevation is temporary or part of a pattern that needs treatment.

Frequently Asked Questions

Can a fever cause permanent high blood pressure?

No. Fever itself does not cause lasting high blood pressure. The spike is temporary and resolves when the fever breaks. However, some serious infections can cause complications that affect blood pressure long-term, so persistent elevation after illness should be evaluated by a doctor.

Should I take blood pressure medication during a fever?

Continue taking your regular blood pressure medication as prescribed unless your doctor tells you otherwise. Do not stop or change doses because of a fever. If you are concerned about how high your reading is, contact your doctor or pharmacist — they can advise whether any adjustment is needed during acute illness.

Is it normal for blood pressure to fluctuate during the day when I have a fever?

Yes. During fever, blood pressure can swing up and down as your body temperature rises and falls, especially if you are taking fever-reducing medication. These fluctuations are expected and not a cause for alarm as long as you do not have warning symptoms like chest pain or shortness of breath.

What if my blood pressure is very high during fever — should I go to the hospital?

Go to the hospital or call emergency services if you have a very high blood pressure reading (usually 180/120 mmHg or higher) combined with chest pain, shortness of breath, severe headache, vision changes, or confusion. If your blood pressure is high but you feel fine otherwise, contact your doctor for guidance rather than assuming it is an emergency.

Can ibuprofen or acetaminophen lower blood pressure as well as fever?

These medications lower blood pressure indirectly by reducing fever and the body's stress response. They do not lower blood pressure directly the way blood pressure medications do. Once the fever is gone, blood pressure should return to baseline on its own.