Why Your Blood Pressure Can Change When You're Sick

When you are sick, your body is busy.

It may be fighting an infection, running a fever, losing fluids, sleeping poorly, coughing nonstop, or wondering why you thought that third cup of coffee was a good idea. Blood pressure can respond to all of that.

So if your usual numbers look different while you have a cold, flu, stomach bug, or another illness, do not panic. But do pay attention.

The important question is not just, “What number did I get?” It is also: How do I feel, is this change repeating, and what else is going on?

Illness can temporarily raise blood pressure for several reasons.

Pain, fever, anxiety, poor sleep, and inflammation can activate your body’s stress response. Your heart may beat faster, and your blood vessels may tighten. That can cause a temporary increase in blood pressure.

Over-the-counter medications can matter, too. Some decongestants—often found in cold and sinus medicines—can raise blood pressure or heart rate. Products that contain pseudoephedrine or phenylephrine deserve a closer look, especially if you have high blood pressure, heart disease, or take blood-pressure medication.

Some pain relievers may also affect blood pressure for certain people. If you have high blood pressure, kidney disease, heart disease, or take prescription medications, it is a good idea to ask a pharmacist or provider which cold and pain products are safest for you.

Illness can also make blood pressure drop.

Vomiting, diarrhea, sweating, fever, or simply not drinking enough can lead to dehydration. When your body has less fluid circulating, you may feel lightheaded, weak, dizzy when standing, or unusually tired.

Not eating normally can also contribute, especially for people taking medicines for blood pressure, diabetes, or heart conditions.

A significant infection can sometimes cause low blood pressure as well. That is more concerning when it comes with severe weakness, confusion, fainting, trouble breathing, chest pain, or a fast heartbeat.

Blood pressure is the force of blood moving through your blood vessels.

Your body constantly adjusts that pressure depending on what is happening. When you are stressed, in pain, or taking a decongestant, your vessels may tighten and pressure can rise. When you are dehydrated, there may be less fluid moving through your circulation and pressure can fall.

That is why one sick-day reading is a clue—not always a conclusion.

If you monitor blood pressure at home, give the reading its best chance to be useful.

Try to:

• Sit quietly for about five minutes first.

• Keep both feet flat on the floor and support your arm at heart level.

• Avoid talking during the reading.

• Use the correct cuff size and place it on bare skin.

• Take two readings about a minute apart and write both down.

• Note symptoms, fever, medications, and whether you are dehydrated or in pain.

Checking immediately after climbing stairs, coughing through the entire reading, or arguing with customer service may not capture your most typical blood pressure. Your cuff is not judging you. It is just collecting data.

In most cases, do not stop, skip, or double your blood-pressure medicine on your own.

That said, some illnesses—especially vomiting, diarrhea, dehydration, or very poor fluid intake—can change what is safest for certain medications. Call your healthcare provider for guidance if you are unable to keep fluids down, feel faint, have very low readings, or are concerned about medication side effects.

Do not use a high reading during an illness as a reason to take extra medication unless a healthcare provider has specifically told you to do that.

Contact a healthcare provider if:

• Your readings stay higher or lower than your usual range after you start feeling better

• You have repeated readings that concern you, even if you feel okay

• You are dizzy, faint, unusually weak, or have trouble staying hydrated

• You are taking a cold medicine and notice higher blood pressure or a racing heartbeat

• You are unsure which over-the-counter medicines are safe with your health conditions or prescriptions

• You have vomiting or diarrhea and take blood-pressure, kidney, heart, or diabetes medications

A provider can help you interpret the pattern and decide whether you need medication guidance, a follow-up visit, or in-person evaluation.

When High Blood Pressure Is an Emergency

A blood pressure reading of 180/120 mm Hg or higher needs prompt attention.

If you get a reading that high, sit quietly and recheck it after a few minutes. If it is still that high, contact a healthcare provider right away for guidance.

Call 911 or seek emergency care immediately if a very high reading comes with chest pain, shortness of breath, severe headache, vision changes, weakness or numbness, confusion, trouble speaking, or severe back pain.

When Low Blood Pressure Needs Urgent Care

Seek urgent medical care for fainting, confusion, severe dizziness, cold or clammy skin, chest pain, trouble breathing, blue lips, or severe weakness—especially during an illness.

These symptoms may be signs that your body needs immediate in-person evaluation.

CallOnDoc providers can review your blood-pressure readings, symptoms, current medications, and any over-the-counter products you are taking through secure online care. If appropriate, they can help you understand whether a medication may be affecting your numbers and whether you need follow-up or in-person care.

Emergency symptoms, severe dehydration, or very high blood pressure with concerning symptoms require immediate in-person evaluation.

Can a cold raise blood pressure?

Yes. Fever, poor sleep, stress, pain, and some cold medicines can temporarily raise blood pressure.

Can dehydration lower blood pressure?

Yes. Dehydration from fever, vomiting, diarrhea, sweating, or poor fluid intake can contribute to low blood pressure and dizziness.

Can I take decongestants if I have high blood pressure?

Some decongestants can raise blood pressure or heart rate. Check with a pharmacist or healthcare provider before using them if you have high blood pressure or heart disease.

Should I check my blood pressure more often when I am sick?

It can be helpful if you have high blood pressure, heart disease, kidney disease, or symptoms such as dizziness or chest discomfort. Focus on trends rather than one isolated reading.

Should I change my medication if my blood pressure changes while I’m sick?

Do not change your dose on your own. Contact your healthcare provider for individualized guidance.

Getting sick can temporarily change your blood pressure in either direction. The best approach is to check carefully, pay attention to symptoms, stay hydrated when you can, and avoid guessing with medications.

If your numbers remain unusual, you feel unwell, or you are not sure which cold medicine is safe for you, a quick conversation with a provider can bring some clarity.