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**High blood pressure, or hypertension, is diagnosed when the pressure of blood through your arteries is higher than normal 1.
If you are experiencing serious medical symptoms, seek emergency treatment immediately.
** Your doctor checks two types of pressure simultaneously–systolic and diastolic. A reading of 120 (systolic) over 80 (diastolic) is normal; 140 over 90 is considered high. Multiple readings must be taken to determine true hypertension 1. If you have hypertension, illness, as well as certain medications that you might take for illness, can cause your high blood pressure to rise even higher 1.
What Causes High Blood Pressure to Rise Higher?
Many things can cause a temporary spike in blood pressure. It can be as simple as a visit to your doctor's office. This type of blood pressure rise is called "white-coat hypertension. "
Another contributory factor to a temporary rise in blood pressure is weather. Blood pressure is naturally higher in winter and lower in summer.
Cold weather causes blood vessels to narrow, constricting blood flow and increasing blood pressure. And illness, particularly illness that is accompanied by fever and infection, can also contribute to a sudden rise in blood pressure.
- Many things can cause a temporary spike in blood pressure.
- Cold weather causes blood vessels to narrow, constricting blood flow and increasing blood pressure.
How Does Illness Cause Blood Pressure to Rise?
Ways to Tell You're Running a Fever
There are a number of ways in which a severe cold or flu, particularly if you are running a fever, can cause a higher blood pressure reading. Anytime you get a fever, your body is working to fight off an infection. Fever raises your temperature, speeds up your heart rate and raises your blood pressure levels. This increased blood pressure is due to "vasoconstriction"– a narrowing of blood vessels. If you have a fever, a blood pressure exam is likely to show that your blood pressure is elevated.
An increase in your heart rate can also occur during other kinds of bacterial or viral infection, including bronchitis, pneumonia and strep throat. This happens in response to your heart's extra oxygen demands, so your system can fight off the infection. A heart-rate increase can also raise your blood pressure. Dehydration from fever or infection can raise your blood pressure, too.
- There are a number of ways in which a severe cold or flu, particularly if you are running a fever, can cause a higher blood pressure reading.
The Cold, the Cure and High Blood Pressure
One way to decrease your risk of a spike in your blood pressure during illness is to check what drugs or medications you are taking.
In addition to the effects of fever, your blood pressure can also be affected by medications. Over-the-counter cold remedies, ones that contain decongestants, are some of the main culprits.
Decongestants work to narrow blood vessels in your nose, helping you breathe more clearly, but they also narrow other blood vessels, raising blood pressure. Decongestants to avoid if you have hypertension include pseudoephedrine, ephedrine, phenylephrine, naphazoline and oxymetazoline 1.
- One way to decrease your risk of a spike in your blood pressure during illness is to check what drugs or medications you are taking.
- In addition to the effects of fever, your blood pressure can also be affected by medications.
Can Other Illnesses Raise Blood Pressure?
Fevers While Pregnant
High blood pressure can result from many different conditions and diseases. These can include diabetes, kidney disease, arteriosclerosis, atherosclerosis and even pregnancy.
Researchers at Beth Israel Deaconess Hospital in Boston reported in the May 15, 2009 issue of PLoS Pathogens, that mice who had been infected with cytomegalovirus (CMV) were likely to experience high blood pressure. CMV is actually a grouping of viruses that infects humans and other animals, including mice. It attacks cells in various organs of the body. CMV infection is wide spread in the human population, affecting some 60 to 99 percent of adults worldwide.
The infection increases the activity of renin, an enzyme that is associated with high blood pressure. It also increases angiotensin 11, a protein associated with high blood pressure.
- High blood pressure can result from many different conditions and diseases.
- The infection increases the activity of renin, an enzyme that is associated with high blood pressure.
Can Illness also Lower Blood Pressure?
As well as contributing to a rise in high blood pressure, illness and severe infections can also result in a quick drop in your blood pressure, known as hypotension. During any serious illness or infection, your doctor will want to monitor your blood pressure regularly. This will help monitor the severity of your illness or infection, as well as the current status of your hypertension 1.
Ways to Tell You're Running a Fever
Fevers While Pregnant
Symptoms of a Low White Blood Count
How to Lower a High Fever in a 6-Month-Old Baby
My Baby's Fever Comes & Goes
Saunas & Bronchitis
When is a Fever Dangerous in Adults?
Fever After Exercise
Drugs That Cause Peripheral Neuropathy
What Happens if You Have High Neutrophils?
- Mayo Clinic: Hypertension
- Beth Israel Deaconess Medical Center: Study Indicates High Blood Pressure Could Be Caused by Common Virus
- American Heart Association. Understanding blood pressure readings.
- American Heart Association. Low blood pressure—when blood pressure is too low. Updated October 21, 2016.
- Centers for Disease Control and Prevention. High blood pressure symptoms, causes, and problems. Updated May 19, 2020.
- Salkic S, Batic-Mujanovic O, Ljuca F, Brkic S. Clinical presentation of hypertensive crises in emergency medical services. Mater Sociomed. 2014;26(1):12-16. doi:10.5455/msm.2014.26.12-16
- Institute for Quality and Efficiency in Health Care (IQWiG). What is blood pressure and how is it measured? InformedHealth.org. Updated May 23, 2019.
- American Heart Association. Know your risk factors for high blood pressure. Updated December 21, 2017.
- Sharma S, Hashmi MF, Bhattacharya PT. Hypotension. StatPearls. Updated May 23, 2020.
- American Heart Association. Health threats from high blood pressure. Updated October 31, 2017.
Kim Norton wrote for 25 years for an in-house securities research publication. She currently writes articles for Demand Studios that involve medical research, law and senior citizen concerns. She also writes radio advertising copy and opera librettos. A graduate of Westminster Choir College, Norton resides in Bayonne, N.J.