Influenza (flu) is a highly contagious respiratory illness caused by a virus that attacks the nose, throat, and lungs. Blood pressure (BP) is the force of blood pushing against artery walls and naturally fluctuates throughout the day. When the body fights a systemic viral infection like the flu, the physiological stress often causes a temporary elevation in blood pressure. This temporary increase is a byproduct of the body’s intense mobilization of its defense systems to combat the pathogen. For individuals managing existing high blood pressure, this temporary spike requires careful monitoring.
The Immediate Physiological Link
The elevation in blood pressure during a flu infection is primarily driven by the body’s generalized inflammatory response. When the immune system detects the influenza virus, it releases chemical messengers called cytokines that signal an active infection. These pro-inflammatory cytokines directly affect the lining of the blood vessels, increasing vascular tone and resistance to blood flow. This systemic inflammation forces the heart to pump harder, contributing to higher blood pressure readings.
Another mechanism involves the release of stress hormones, such as cortisol and adrenaline, which surge as the body fights the illness. These hormones naturally cause the heart rate to increase and blood vessels to constrict, a process known as vasoconstriction. Furthermore, fever and associated symptoms like vomiting or diarrhea can lead to dehydration, complicating BP regulation. Dehydration causes the body to release hormones like vasopressin to conserve water, which further constricts blood vessels and raises blood pressure. The combined effect of inflammation, hormonal stress, and reduced fluid volume places considerable strain on the cardiovascular system.
Medications and Blood Pressure Management During Flu
Individuals with pre-existing hypertension must exercise caution when selecting over-the-counter (OTC) flu and cold remedies, as many common ingredients interfere with blood pressure control. Decongestants, such as pseudoephedrine and phenylephrine, are a particular concern because they narrow blood vessels in the nasal passages to relieve congestion. When absorbed systemically, these drugs cause generalized vasoconstriction throughout the body, directly increasing blood pressure. Pseudoephedrine affects both alpha and beta receptors, which can significantly raise the heart rate and systemic blood pressure.
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs), including common pain relievers like ibuprofen and naproxen sodium, also require careful consideration. NSAIDs cause the body to retain sodium and fluid, a side effect that directly leads to elevated blood pressure. For those taking blood pressure medications like ACE inhibitors, Angiotensin Receptor Blockers (ARBs), or diuretics, combining them with NSAIDs can be particularly dangerous. This combination, known as the “triple whammy,” can impair kidney function and counteract the prescribed medicine’s blood pressure-lowering effects. Acetaminophen is considered a safer alternative for managing fever and body aches in individuals with hypertension. Always consult a pharmacist or physician before taking any combination cold and flu product.
When to Seek Medical Attention
While a temporary rise in blood pressure is expected with the flu, a sustained, significant elevation requires immediate medical attention. A blood pressure reading of 180 millimeters of mercury (mm Hg) systolic or 120 mm Hg diastolic or higher is defined as a hypertensive crisis. If a person records readings at or above this threshold without symptoms of organ damage, it is considered hypertensive urgency, and a healthcare professional should be contacted right away.
The situation escalates to a hypertensive emergency if a reading of 180/120 mm Hg or greater is accompanied by severe symptoms indicating potential organ damage. These warning signs require an immediate call to emergency services. Prompt recognition of these signs is essential for preventing serious complications like stroke or heart attack caused by uncontrolled blood pressure.
Symptoms of Hypertensive Emergency
- Sudden, severe headache
- Chest pain
- Shortness of breath
- Neurological changes (numbness, weakness, difficulty speaking)
- Sudden changes in vision