Does Shivering Raise Blood Pressure?

Shivering reliably raises blood pressure in most people. The involuntary muscle contractions that characterize shivering increase the body’s metabolic demand, trigger a surge in stress hormones like norepinephrine, and activate the sympathetic nervous system, all of which push blood pressure upward. The size of the rise depends on age, cardiovascular health, and the severity of the cold challenge, but the direction of the effect is consistent across decades of research.

Why Shivering Drives Blood Pressure Up

When your core temperature starts to drop, the body mounts a defense on two fronts. First, blood vessels near the skin constrict to keep warm blood closer to your organs. Second, skeletal muscles begin contracting rapidly and involuntarily, generating heat through shivering. Both of these responses are orchestrated by the sympathetic nervous system, the same “fight or flight” branch that revs up when you are startled or stressed.

Research on core cooling in healthy adults has shown that shivering drives up metabolic rate while norepinephrine-mediated vasoconstriction raises mean arterial blood pressure. Heart rate, interestingly, often stays about the same, so the pressure increase comes mainly from the blood vessels tightening rather than the heart beating faster.¹ At the same time, circulating catecholamines, the chemical messengers that tell your blood vessels to constrict, rise measurably during shivering episodes.²

Cold exposure also ramps up sympathetic nerve activity to the kidneys, which plays a role in regulating blood pressure over longer periods. Animal research has found that renal sympathetic nerve activity increases immediately on cold exposure and keeps climbing over days, even remaining elevated after the cold stimulus ends.³ While that study focused on sustained cold rather than a brief bout of shivering, it points to a broader pattern: the cardiovascular system does not simply flip a switch when you get cold and flip it back when you warm up. There is a lingering sympathetic activation that can outlast the exposure itself.

Even Without Shivering, Cold Raises Blood Pressure

Shivering is only one of the body’s cold-defense mechanisms. You can be cold enough to trigger significant cardiovascular changes without shivering at all. A study of healthy adults exposed to mild cold designed to activate brown fat rather than provoke shivering found that both systolic and diastolic blood pressure rose, going from roughly 127 to 132 systolic and 82 to 85 diastolic on average. Plasma noradrenaline more than doubled during the same exposure.⁴

This matters because it shows the blood pressure rise is not caused by the physical act of shivering alone. The sympathetic nervous system activation from cold perception can raise pressure before a single muscle tremor begins. Shivering adds to this baseline effect by piling metabolic demand and additional stress-hormone release on top of the vasoconstriction that is already happening. Think of it as two layers: cold constricts the pipes, and shivering turns up the pump. Either one raises pressure, but together the effect is larger.

The Age Factor

Older adults see a bigger blood pressure spike from cold exposure than younger people, and the difference is substantial. In studies comparing young and older subjects during cold challenges, the older group consistently showed higher blood pressure at baseline in the cold and larger increases as the exposure continued.⁵ The rise in both systolic and diastolic pressure was significantly greater in older men exposed to cold.⁶

A key explanation is arterial stiffness. As arteries stiffen with age, they lose the ability to buffer surges in pressure. A study measuring aortic pulse wave velocity, a standard marker of arterial stiffness, found that pre-cooling stiffness explained about 63% of the variation in how much blood pressure rose during cold stress in older adults.⁷ In other words, the stiffer your arteries already are, the harder the cold will push your blood pressure up. This is one reason that cold weather has long been associated with increased rates of heart attacks and strokes in older populations.

Younger people, by contrast, tend to have more compliant arteries that can absorb the vasoconstriction without as dramatic a pressure rise. Their shivering response may be just as vigorous, but the cardiovascular system handles the added strain more gracefully.

When Shivering Becomes Dangerous After Surgery

The blood pressure story gets more complicated in the operating room. Patients who have undergone major surgery, especially cardiac surgery involving cardiopulmonary bypass, are often mildly hypothermic when they arrive in the recovery unit. As they rewarm, shivering can become intense. But in these patients, the cardiovascular effects of shivering go beyond simply raising blood pressure. The metabolic demand can overwhelm a heart that is already recovering from surgery.

In one study of patients rewarming after cardiac bypass, those who shivered had significantly higher oxygen consumption and carbon dioxide production, along with a higher heart rate and cardiac index. Their mixed venous oxygen saturation dropped, a sign the body was consuming oxygen faster than the heart could deliver it.⁸ For someone with impaired heart function after surgery, this kind of metabolic surge can be genuinely harmful.

In another trial comparing patients whose postoperative shivering was pharmacologically suppressed to those who shivered freely, the shivering group showed hemodynamic instability marked by lower systolic blood pressure, lower mixed venous oxygen saturation, and a greater need for drugs to support the heart’s pumping ability.⁹ That might seem to contradict the idea that shivering raises blood pressure. The difference is context: in a healthy person, the heart can meet the extra demand and pressure goes up. In a post-surgical patient whose heart is compromised, the demand outstrips supply and the system destabilizes, sometimes with blood pressure dropping rather than rising because the heart simply cannot keep up.

A neurosurgery-specific study echoed these findings. Patients whose shivering was prevented with nefopam had lower left ventricular workload and lower oxygen consumption compared to controls who shivered.¹⁰ Preventing shivering in these settings is not about comfort. It is about reducing cardiovascular strain during a vulnerable period.

How Hospitals Manage Shivering-Related Blood Pressure Changes

Because shivering can destabilize cardiovascular function in patients who are already fragile, hospitals use several strategies to control it. The most common involve warming the patient externally with forced-air blankets or pharmacologically suppressing the shivering reflex.

On the drug side, two approaches are worth noting. Meperidine, an opioid, has long been used to treat postoperative shivering because it lowers the shivering threshold. Alpha-2 adrenergic agonists like dexmedetomidine work differently: they dampen the sympathetic nervous system activity that drives both the shivering and the blood pressure response. In one trial involving patients who had undergone cesarean sections, dexmedetomidine produced more stable blood pressure readings than meperidine across multiple time points during recovery.¹¹ The logic is straightforward: if shivering raises blood pressure partly through sympathetic activation and catecholamine release, a drug that blunts the sympathetic response should blunt the blood pressure spike as well.

In the emerging field of therapeutic hypothermia, where patients with brain injuries are deliberately cooled to protect the nervous system, shivering is one of the main complications that clinicians must manage. It is considered a potentially damaging side effect of the treatment itself, precisely because of the cardiovascular strain it imposes.¹² The irony is that cooling the patient is neuroprotective, but the body’s own fight against the cooling can harm the heart.

Shivering Makes Blood Pressure Hard to Measure

Here is a practical wrinkle that rarely gets mentioned: shivering can make your blood pressure reading unreliable. The involuntary muscle contractions create motion artifacts that interfere with both manual and automated blood pressure cuffs. One engineering study specifically identified shivering as an external source of measurement inaccuracy alongside sudden arm motion and vehicle vibrations during patient transport.¹³

So if you are shivering while getting your blood pressure checked, the reading may be artificially high for two reasons. First, your blood pressure actually is elevated because of the sympathetic response. Second, the tremor in your arm muscles is introducing noise into the measurement. Medical staff are generally trained to let a patient warm up before taking a reading, but in emergency settings or field medicine, that is not always possible. If you have ever gotten a surprisingly high reading at a clinic where the waiting room was freezing, this combination of genuine physiological response and measurement artifact is a plausible explanation.

Cold Acclimatization and Whether the Effect Fades

People who spend extended time in extreme cold environments show some interesting adaptations. A classic study followed four men who moved from Australia to Antarctica, testing their responses to a standard cold exposure before and after about six months at the polar station. After acclimatization, their bodies were better at maintaining core temperature during the cold test. Their heart rate response to cold shifted, with a more pronounced slowing of the heart. But the rise in blood pressure from cold exposure did not change.¹⁴

This suggests that while the body can adapt to cold in some ways, the blood pressure response remains stubbornly intact. The vasoconstriction and sympathetic activation triggered by cold seem to be baked into the response in a way that months of polar living do not override. Whether this means the blood pressure response serves an essential survival function or simply reflects an inflexible reflex arc is an open question. Either way, you should not assume that “getting used to the cold” will protect you from the cardiovascular effects.

Everyday Situations Where This Matters

For most healthy people, the blood pressure rise from a bout of shivering is temporary and harmless. Your body shivers, pressure goes up a few points, you warm up, and everything returns to normal. The concern arises in specific populations and situations:

Older adults in winter: The combination of stiffer arteries and a more pronounced pressor response means that even routine cold exposure, like walking to the car on a freezing morning, can push blood pressure substantially higher. For someone already on the edge of hypertensive crisis, this is not trivial.
People with heart disease: The increased oxygen demand from shivering forces the heart to work harder. If the coronary arteries are narrowed, this can tip the balance toward ischemia, where the heart muscle is not getting enough blood flow.
Post-surgical patients: As described above, shivering after surgery can cause hemodynamic instability that threatens recovery.
People taking blood pressure medication: Beta-blockers and other antihypertensives may blunt some of the cardiovascular response to cold, but they can also impair the body’s ability to generate heat, potentially prolonging the cold challenge.

For anyone in these groups, simple measures like dressing warmly, preheating the car, and avoiding prolonged cold exposure are not just comfort tips. They are cardiovascular protection strategies. The blood pressure rise from shivering is real, reproducible, and in the right circumstances, clinically meaningful.

Why Blood Pressure Readings Vary by Season

Cardiologists and epidemiologists have long noticed that blood pressure tends to run higher in winter months across entire populations. Part of this is behavioral: people exercise less, eat differently, and may gain weight. But the direct physiological effect of cold on the sympathetic nervous system is a major contributor. Cold-related morbidity and mortality, including cardiovascular and cerebrovascular events, have been documented as a public health concern that climate change is expected to complicate in unpredictable ways.¹⁵

The shivering-blood pressure connection is one thread in a larger tapestry linking temperature and cardiovascular health. Even in regions where winters are mild, short-term dips in temperature are associated with bumps in hospital admissions for heart-related events. The mechanism runs through the same sympathetic pathways that produce the shivering response: cold activates the nervous system, vessels constrict, pressure rises, and the heart works harder. For most of the population this is a minor and transient stress. For millions of people with underlying cardiovascular disease, it represents a recurring seasonal challenge that is worth understanding and managing.