Does Blood Sugar Affect Blood Pressure?

Is it mere coincidence that so many people have both high blood pressure (hypertension) and diabetes? These two conditions are often found in the same people, with each considered a “comorbidity” of the other (meaning a condition that commonly accompanies another condition). For example, if you have diabetes—a disorder in which you have too much sugar, or glucose, in your blood—you are twice as likely to also have hypertension as someone who doesn’t have diabetes, as noted in a review article in the Canadian Journal of Cardiology. And people who have high blood pressure are more likely to have insulin resistance, a key risk factor for type 2 diabetes, compared to the general population.

How exactly are high blood sugar and high blood pressure related? Does one cause the other? Or do they stem from the same underlying cardiometabolic issues? We talked to experts about the interplay between these two important health markers.

“We believe that the common combination of diabetes and hypertension is no coincidence,” says Fiona McBryde, Ph.D., a senior lecturer at the Manaaki Manawa Centre for Heart Research at the University of Auckland in New Zealand. McBryde is part of an international research team that in 2022 published preliminary findings suggesting that both blood pressure and blood sugar are mediated by a small sensor in the neck called the carotid body.

“We think that changes within the carotid body can end up causing an inappropriate, long-term activation of the sympathetic nervous system,” says McBryde. Designed to prepare you for “fight or flight” when you’re under threat, the sympathetic nervous system releases hormones such as adrenaline that result, among other things, in increased heart rate and blood pressure (via constricting your blood vessel) as well as a release of glucose into the blood for quick energy. If further research confirms the team’s findings, then a shared underlying cause of both high blood pressure and high blood glucose will have been found, which could have important implications for treatment.

The two conditions are already known to share some of the same causes and risk factors, including:

• Chronic inflammation

• Insulin resistance

• Obesity

• Overproduction of tissue-damaging free radicals

• Sedentary lifestyle

Blood sugar may directly influence blood pressure, too. “High blood sugar can worsen and potentiate high blood pressure through several means,” says Ian Neeland, M.D., an associate professor of medicine at Case Western Reserve University School of Medicine in Cleveland, OH. For example, untreated high blood sugar damages blood vessels so that the walls stiffen, become narrower, and accumulate plaque, a process called atherosclerosis. Depending on which arteries are affected, atherosclerosis can lead to high blood pressure, per the National Heart, Lung, and Blood Institute (NHLBI), a division of the NIH.

In addition, chronic high blood sugar leads to long-term high insulin levels that can increase blood pressure via a variety of mechanisms, explains Dr. Neeland. These include activating the sympathetic nervous system as well as causing the kidneys to decrease their reabsorption of water and sodium. The latter in turn increases blood volume, which puts more pressure on blood vessel walls.

Interestingly, low blood sugar (hypoglycemia)—which can be a side effect of some diabetes medications—can also increase blood pressure. “Low blood sugar caused by medications, such as insulin and sulfonylureas [such as glipizide], stimulates a stress response including the secretion of glucagon and epinephrine,” explains Matthew J. Freeby, M.D., director of the Gonda Diabetes Center and associate director of diabetes clinical programs at the David Geffen UCLA School of Medicine in Los Angeles. These hormones not only spur the liver to make glucose, but they also “typically cause blood pressure and heart rate to rise concomitantly,” Dr. Freeby says.

“Multiple hormones are in charge of regulating blood sugar levels on a regular basis,” says Dr. Neeland. Two of the most important are insulin and glucagon, which work together to keep blood sugar in a narrow range. If blood sugar falls too low, Dr. Neeland notes, the body will produce what are called “gluco-counter-regulatory” hormones. These hormones, which include glucagon as well as epinephrine (adrenaline), cortisol, and growth hormone, act through different mechanisms to increase blood sugar levels. On the other hand, “if blood sugar rises too high (hyperglycemia), the body produces insulin. This hormone drives sugar out of the bloodstream into the muscle and fat, ultimately decreasing blood sugar,” Dr. Neeland says.

Numerous factors can affect your blood sugar over the course of the day. They include:

• Food choices. Some foods and beverages cause a large rise in blood sugar after eating them, while others help keep blood sugar more stable. The effect of a given food on blood sugar is called the glycemic index.

• Illness. Even something as simple as a cold can increase blood sugar levels, Dr. Freeby notes: “Generally, this occurs via a rise in stress hormones, such as cortisol, glucagon, and epinephrine,” he says.

• Lack of sleep

• Skipping meals (this can lead to low blood sugar, especially in people taking insulin to treat diabetes)

• Stress

• Underlying problem with the pancreas, the gland that makes insulin

The body has elaborate feedback mechanisms to regulate blood pressure, in part by constricting (narrowing) or dilating (widening) the blood vessels. These include various nerves and hormones such as adrenaline. “The body regulates blood pressure by several mechanisms, including by many of the same that help manage blood sugar,” says Dr. Neeland, adding that hormones that can increase blood pressure include aldosterone, cortisol, adrenaline, and insulin.

Meanwhile, hormones and regulators such as nitric oxide, natriuretic peptides, and vasodilator peptides (peptides are small chains of amino acids, the building blocks of protein) cause blood vessels to dilate, or expand, which in turn lowers blood pressure. High blood sugar, as seen in people with diabetes, is associated with a reduction in the production of nitric oxide and the two peptides, which over time can lead to hypertension.

Dr. Neeland notes that many variables over the course of the day can affect your blood pressure. Factors that can raise blood pressure include:

• Drinking beverages containing caffeine

• Not getting enough sleep

• Smoking

• Stress

• Taking certain medications such as decongestants

Factors that can cause a drop in blood pressure include:

• Being dehydrated

• Drinking alcohol

• Taking certain medications such as beta-blockers (prescribed for heart failure and anxiety, among other uses) or drugs for erectile dysfunction

• Standing up quickly from a lying down position

“High blood pressure remains the number one controllable risk factor for heart disease and stroke in adults,” says Christianne Roumie, M.D., an associate professor of internal medicine and pediatrics at Vanderbilt University Medical Center in Nashville, TN. The litany of consequences that result from hypertension is vast, according to Dr. Neeland, and includes coronary heart disease, heart failure, kidney disease, eye disease, peripheral vascular disease, and life-threatening aortic disease such as aneurysm (in which the blood vessel walls become weak and bulge outward) or dissection (a tear in a vessel’s inner wall).

In contrast, “the consequences of low blood pressure, or hypotension, are generally acute rather than chronic and include dizziness, lightheadedness, passing out, and fatigue,” says Dr. Neeland. There can be long-term damage in some cases, however; for example, if you lose a lot of blood from an accident, your blood pressure can drop and if not treated quickly, the insufficient blood flow can result in damage to the kidneys and other organs.

“High blood pressure can be prevented through lifestyle means such as exercise, a healthy diet (low in sodium, rich in fruits and vegetables), a healthy weight, and adequate sleep,” says Dr. Neeland. “Diet and exercise can often lower blood pressure as much as starting a medication, but if high blood pressure has been present for a while, medications are often needed along with diet and exercise,” adds Dr. Roumie.

As for low blood pressure, “it can be avoided by ensuring good hydration, adequate nutrition, and avoiding illness,” says Dr. Neeland. According to the American Heart Association, various nutrient deficiencies, including inadequate vitamin B12 and folate, might be linked with low blood pressure.

If you’re being treated with medication for hypertension, tell your healthcare provider if you have any of the symptoms of low blood pressure. Sometimes it requires medication adjustments to find the right dose and regimen.

If you have both hypertension and diabetes, you need to monitor both of these vigilantly. “High blood pressure is more difficult to control in patients with diabetes, so you will probably need to take two or more different types of medication to keep your blood pressure under control,” says McBryde. Your best bet is to work closely with your healthcare team to find the right regimen of lifestyle steps and medications to keep both your blood sugar and blood pressure in the healthy range.