A cold or flu can temporarily push blood pressure higher, sometimes meaningfully so. The increase comes from several directions at once: your immune system’s inflammatory response, the stress your body is under, and often the medications you reach for to feel better. For most people, the bump is modest and resolves as you recover. But for anyone already managing high blood pressure or heart disease, even a routine respiratory infection deserves a closer look than it usually gets.
What Infection Does to Your Blood Vessels
When a virus takes hold, your immune system launches an inflammatory cascade. Proteins called cytokines flood the bloodstream, and your sympathetic nervous system ramps up, raising your heart rate and tightening blood vessels. These are survival responses, designed to help your body fight the invader, but they also push blood pressure upward.
Inflammation also stiffens the lining of your blood vessels. In a study using a typhoid vaccine to safely trigger an inflammatory response in healthy volunteers, researchers measured how well participants’ arteries could relax. The entire group showed reduced blood-vessel flexibility, dropping from about 11% to roughly 8% dilation in younger adults. In older adults, the effect started from a lower baseline and still dropped further.
What was especially interesting was how blood pressure responded differently by age. Younger adults saw their pulse pressure increase (the gap between the top and bottom numbers widened), while older adults actually saw a drop in systolic pressure alongside the inflammatory challenge. The researchers attributed this to aging itself rather than to the inflammation, suggesting that older blood vessels respond to the same immune signals in a less predictable way.1Journal of Hypertension. Aging, not age-associated inflammation, determines blood pressure and endothelial responses to acute inflammation The takeaway is that inflammation from illness genuinely impairs your blood vessels’ ability to regulate pressure, and the effect can last at least a couple of days.
Coughing Itself Creates Pressure Spikes
Beyond what infection does to your immune system, the physical act of coughing generates abrupt increases in blood pressure. Each cough rapidly raises the pressure inside your chest, which in turn pushes blood pressure up sharply for a few seconds. In a study of patients who had their blood pressure and heart rate monitored continuously during coughing episodes, systolic pressure jumped from an average of about 137 to 176 mmHg, and diastolic pressure rose from roughly 72 to 84 mmHg.2PubMed. Effect of abruptly increased intrathoracic pressure on coronary blood flow velocity in patients
These spikes are brief and typically harmless in someone with healthy blood vessels. But if you already have high blood pressure or weakened arteries, repeated forceful coughing over days can be more than a nuisance. It is one reason a lingering cough from bronchitis or a chest cold can leave you feeling genuinely exhausted and unwell beyond what the infection alone would explain.
The Medications You Take May Matter More Than the Virus
Here is where the story gets more practical, and where a lot of people get tripped up. When you are sick, you reach for cold and flu remedies, and some of them affect blood pressure in ways the infection itself may not.
Decongestants
Oral decongestants like pseudoephedrine and phenylephrine are the usual suspects. They work by constricting blood vessels in your nasal passages, which is why they unstuff your nose, but they can constrict blood vessels elsewhere too. Doctors have cautioned against them for people with high blood pressure for decades.
The actual evidence, though, is more nuanced than the warnings suggest. A Cochrane review of randomized trials found that oral decongestants had little to no measurable effect on systolic or diastolic blood pressure compared to placebo, with average differences of less than 1 mmHg for both. The authors were careful to note, however, that the evidence was of very low to low certainty, meaning the studies were small or inconsistent enough that the true effect could be larger than what was measured.3Cochrane Library. Effect of adrenergic agonist oral decongestants on blood pressure In other words, the average person taking a standard dose of pseudoephedrine for a few days probably won’t see a big jump on a blood pressure cuff, but individual reactions vary, and the research is not strong enough to be fully reassuring for someone whose blood pressure is already hard to control.
Pain Relievers and Anti-Inflammatories
NSAIDs like ibuprofen and naproxen are a different story. These drugs reduce pain and fever effectively, but they also interfere with how your kidneys handle sodium and water. The result can be fluid retention, which raises blood pressure. This effect is well-documented: by blocking prostaglandin production in the kidneys, NSAIDs cause sodium retention that can lead to edema and higher blood pressure readings.4Electrolytes & Blood Pressure. Electrolyte and Acid-Base Disturbances Associated with Non-Steroidal Anti-Inflammatory Drugs For someone already on blood pressure medication, NSAIDs can partially cancel out the effect of those drugs. Acetaminophen (paracetamol) is generally considered the safer alternative for pain and fever during illness if blood pressure is a concern, though it is not entirely neutral either, as we will see.
The Hidden Sodium in Effervescent and Soluble Tablets
This is the least appreciated medication pitfall during illness, and arguably the most significant one. Many people reach for effervescent or soluble forms of common medications, things like fizzy vitamin C tablets, soluble cold-and-flu powders, or dissolvable paracetamol. These formulations contain sodium-based excipients (sodium bicarbonate or sodium carbonate) to make the tablets dissolve. The sodium content can be surprisingly high.
A crossover trial comparing standard paracetamol tablets with effervescent paracetamol found that the effervescent version raised 24-hour systolic blood pressure by about 4 mmHg on average compared to regular tablets. In the per-protocol analysis, the gap widened to about 5 mmHg.5Journal of Hypertension. Effect of effervescent paracetamol on blood pressure: a crossover randomized clinical trial That may sound small, but sustained over days of illness, and stacked on top of the other blood-pressure-raising effects already in play, it adds up.
In patients who were regularly taking effervescent medications and already had high blood pressure, simply switching to non-effervescent tablets brought systolic pressure down by about 13 mmHg and diastolic pressure down by about 2.5 mmHg. These patients had been consuming around 74 mmol of sodium per day just from their medication, a substantial hidden salt load on top of whatever they were eating.6PubMed. Blood pressure reduction in hypertensive patients after withdrawal of effervescent medication A large nested case-control study reinforced the concern: patients prescribed sodium-containing effervescent, dispersible, or soluble drugs had dramatically higher odds of developing hypertension compared to those taking the same active ingredients in non-sodium formulations.7BMJ. Association between cardiovascular events and sodium-containing effervescent, dispersible, and soluble drugs: nested case-control study
The practical lesson is simple: if you have high blood pressure, or you are worried about blood pressure during illness, check the formulation. Standard tablets or capsules contain little to no sodium. Effervescent and soluble versions of the same drug can contain a day’s worth of extra salt.
Flu and Heart Attack Risk
The blood-pressure effects of a cold or flu are one thing. The cardiovascular danger from influenza specifically is another, and it goes well beyond a few extra points on a blood pressure reading. Flu has been consistently linked to a sharp, short-lived spike in heart attack risk.
A landmark Canadian study matched laboratory-confirmed influenza diagnoses with hospital admissions for heart attack in the same patients. In the first seven days after a confirmed flu diagnosis, the rate of heart attacks was about six times higher than during comparable control periods in the same individuals.8PubMed. Acute Myocardial Infarction after Laboratory-Confirmed Influenza Infection After the first week, the elevated risk vanished.
A recent systematic review and meta-analysis confirmed this pattern across multiple studies. The pooled risk of heart attack in the first one to three days after flu was nearly sevenfold higher, dropping to about fivefold during days four through seven, and then tapering to roughly double during the second week before returning close to baseline by the end of the first month.9PubMed Central. The association between influenza infection and acute myocardial infarction: A comprehensive systematic review and meta-analysis An earlier systematic review of observational studies across different settings and methods had also reported consistent associations between influenza and acute heart attacks.10PubMed. Influenza as a trigger for acute myocardial infarction or death from cardiovascular disease: a systematic review
The mechanism is thought to involve the combination of inflammation destabilizing plaques in coronary arteries, increased blood clotting tendency during acute infection, and the hemodynamic stress from fever, dehydration, and elevated heart rate. Blood pressure spikes may contribute, but they are just one piece of a broader cardiovascular storm that influenza can trigger. This is not a theoretical concern: the week after a flu diagnosis is a genuinely dangerous window for people with existing heart disease.
Dehydration and Fever
Fever increases your body’s water losses through sweating and faster breathing. Poor appetite means you may not be drinking or eating enough to replace what you are losing. For most healthy adults, mild dehydration during a cold is unpleasant but manageable. For older adults, dehydration during illness poses a more serious risk to blood pressure stability.
Elderly people are already more vulnerable to fluid imbalances because of age-related changes in kidney function and thirst signaling. When an infection adds fever and reduced fluid intake on top of that, blood volume can drop enough to cause blood pressure to swing unpredictably, sometimes too high and sometimes too low.11SpringerLink. Preventing and treating dehydration in the elderly during periods of illness and warm weather If an older person is also taking blood pressure medication, which itself promotes fluid loss, the combination can produce dangerously low readings when standing up (orthostatic hypotension) alongside higher-than-usual readings while lying down. The practical advice for older adults during any febrile illness is to prioritize fluid intake and to be cautious about position changes.
Stress, Anxiety, and the “Feeling Awful” Effect
Being sick is stressful. You feel terrible, sleep poorly, worry about missing work, and spend days in a state of physical discomfort. All of this activates the same stress pathways that drive up blood pressure in other situations. Anxiety alone has been shown to raise blood pressure in the short term, and the “white coat effect,” where a person’s blood pressure jumps simply from the stress of being measured, is a classic example of how psychological state influences readings.12PubMed Central. Association between anxiety and hypertension: a systematic review and meta-analysis of epidemiological studies
If you take your blood pressure at home while you are in the middle of a miserable cold, the reading is going to reflect not just the infection but also your disrupted sleep, your elevated stress hormones, and possibly the medications you have taken. A reading that is 10 or 15 points higher than your usual baseline during a week of illness is not necessarily a sign that your blood pressure has fundamentally changed. It is a snapshot of your body under multiple forms of stress at once. That said, if you consistently see readings above 180/120, or if you develop symptoms like chest pain, vision changes, or severe headache, that warrants medical attention regardless of whether you think it’s “just the flu.”
Can a Virus Cause Lasting Blood Pressure Changes?
For most respiratory infections, the answer is no. Blood pressure typically returns to its usual baseline within a few days to a couple of weeks after recovery. But some viral infections appear capable of leaving a longer imprint on cardiovascular regulation.
The clearest recent example comes from COVID-19. Research on patients who developed postural tachycardia syndrome (POTS) after COVID found that these individuals had higher average 24-hour and nighttime systolic blood pressure compared to population controls, along with disruptions in the normal circadian pattern of blood pressure that is supposed to dip during sleep.13PubMed Central. Blood Pressure Regulation in Post-COVID POTS: Beyond Sinus Tachycardia These patients also experienced more episodes of low blood pressure during the day, suggesting the entire regulatory system had been thrown off rather than simply pushed in one direction.
Whether ordinary cold or flu viruses can produce similar lasting effects is less clear. Most people recover without any persistent cardiovascular changes. But the post-COVID data is a useful reminder that viral infections are not always benign bystanders to the cardiovascular system, and it is worth paying attention to your blood pressure during recovery, not just during the acute illness.
Flu Vaccination and Cardiovascular Protection
If the flu is this hard on the heart, does preventing it actually reduce cardiovascular events? The evidence here is surprisingly strong. A meta-analysis of clinical trials found that influenza vaccination reduced the risk of major cardiovascular events by about 30% compared to placebo.14PubMed Central. Influenza vaccination and major cardiovascular risk: a systematic review and meta-analysis of clinical trials studies
A separate systematic review combining data from both randomized trials and observational studies in patients with existing cardiovascular disease found that influenza vaccination was associated with a 25% lower risk of dying from any cause, an 18% lower risk of dying specifically from cardiovascular causes, and a 13% lower risk of major cardiovascular events like heart attacks and strokes.15PubMed Central. Effects of Influenza Vaccine on Mortality and Cardiovascular Outcomes in Patients With Cardiovascular Disease: A Systematic Review and Meta-Analysis The effect sizes are in the same range as some secondary-prevention drugs that are considered standard of care in cardiology, which is why major cardiology guidelines now recommend annual flu vaccination for patients with heart disease.
This is not about blood pressure in isolation. It is about the entire inflammatory, prothrombotic, hemodynamic package that influenza delivers to the cardiovascular system. Preventing the infection prevents the whole cascade.
What to Do When You Are Sick and Worried About Blood Pressure
If you manage hypertension and catch a cold or flu, a few straightforward steps can keep things under control. First, do not stop taking your regular blood pressure medications. Some people worry about low blood pressure if they are not eating or drinking enough, but abruptly stopping antihypertensives is almost always riskier than continuing them. If you are concerned about dehydration or dizziness, call your doctor before making changes.
Second, choose your cold remedies carefully. Acetaminophen in regular tablet or capsule form is the lowest-risk option for fever and pain. Avoid effervescent or soluble formulations of any medication if you can, since the hidden sodium adds up fast. If you need a decongestant and your blood pressure is well controlled, a short course is probably fine, but check with your provider if you are on multiple medications or if your blood pressure has been hard to manage.
Third, stay hydrated. This does not mean forcing fluids beyond what is comfortable, but it does mean making a deliberate effort to drink regularly, especially if you have a fever. Water, broth, and diluted juice all count. Caffeinated drinks and alcohol are counterproductive.
Fourth, if you are monitoring at home, expect your readings to be higher than usual and do not panic over a few elevated numbers. What you are watching for is sustained severe elevation (above 180 systolic or above 120 diastolic) or any symptoms suggesting a hypertensive emergency: severe headache, chest pain, shortness of breath out of proportion to your respiratory illness, or visual disturbances. Those need immediate medical attention.
Finally, take recovery seriously. The highest cardiovascular risk from influenza is concentrated in the first week after diagnosis. Pushing yourself back to normal activity while still febrile or symptomatic is not stoic; it is medically unwise. Rest during acute illness is not optional for people with cardiovascular risk factors. It is part of how you protect your heart.