Does blood sugar affect heart rate?
Yes, and learning exactly what changes occur can help you better manage your cardiovascular health.
Does your blood sugar affect your heart rate? In a word: Yes. Although experts don’t have a complete picture of the connection between the two, it’s becoming increasingly clear that a relationship exists. In fact, blood sugar may affect heart rate in the short and long term. For most healthy people, this is typically not a problem, but in some cases, it may put you at risk for cardiac irregularities.
Here’s the essential information you should know to stay healthy.
What are blood sugar and heart rate?
Blood sugar, or blood glucose, refers to the amount of glucose (a simple sugar, or monosaccharide) circulating in your bloodstream. Blood sugar levels are influenced primarily by what you eat, along with factors like stress, physical activity, and your sleep schedule. Your body is equipped to get blood sugar back to baseline when it rises after eating and falls after fasting. However, repeatedly spiking your blood sugar with high-carb, high-sugar foods makes this balancing act difficult and contributes to a range of problems, including cardiovascular issues.
Blood glucose can be measured with a fasting blood glucose test ordered by your doctor, or you can use a continuous glucose monitor (CGM) to see how blood sugar fluctuates in real time. For people without diabetes, fasting blood glucose of 70 to 99 mg/dL is normal (though 72 to 85 mg/dL may be optimal), and post-meal blood glucose should ideally not exceed 140 mg/dL.
Heart rate simply refers to the rate at which your heart beats, expressed in beats per minute (bpm). The heart’s electrical system (called the cardiac conduction system) regulates heart rate. This system is directly controlled by the two branches of the autonomic nervous system: the sympathetic nervous system, SNS, which stimulates the release of norepinephrine and epinephrine to increase heart rate, and the parasympathetic nervous system, PNS, which stimulates the release of acetylcholine to lower heart rate. So, anything that activates or suppresses either of these branches can influence heart rate.
You can check your heart rate on a wearable device like a smartwatch or by feeling for your pulse on your wrist and counting the beats in one minute. Resting heart rate (RHR) is your heart rate when you aren’t exerting yourself (think: when you’re sleeping, reading, or working at a desk). “Normal” RHR is 60 to 100 bpm, per the American Heart Association, though a lower heart rate generally indicates better cardiovascular fitness. For accurate readings, wait at least an hour after exercise or stressful events to check RHR.
It’s natural for both blood sugar and heart rate to fluctuate throughout the day due to activity, food, and stress. But in general, you want to avoid spiking blood sugar more than 30 mg/dL from pre-meal levels, and you ideally want resting heart rate to remain in the 55 to 85 bpm range.
How does blood sugar affect heart rate in the short term?
Both low blood sugar (hypoglycemia) and eating a high-carb meal (which can prompt a blood sugar spike, or hyperglycemia) have the potential to elevate your heart rate and trigger heart palpitations. While it can be surprising and unsettling to feel like your heart is pounding, racing, or skipping beats, these sensations typically resolve once blood sugar stabilizes and are not necessarily a cause for concern. Instead, consider them a reminder to keep meals balanced.
First, let’s explore low blood sugar. While it’s far less likely for a person without diabetes to experience hypoglycemia compared to someone with diabetes who is taking insulin or another type of glucose-lowering medication, it’s not impossible. For example, if you’ve gone longer than usual without eating and your body hasn’t developed the metabolic flexibility to efficiently burn fat and ketones instead of glucose, your blood sugar levels could potentially dip. You could also experience reactive hypoglycemia. This is when the body releases a surge of insulin in response to a very sugary or very high-carb meal, which causes blood sugar to drop too low.
In either case, the brain senses an “energy crisis” from the glucose dip, which triggers the sympathetic nervous system (i.e., the fight-or-flight response). This can prompt the release of hormones like epinephrine (adrenaline), cortisol, and glucagon to mobilize glucose from stored glycogen in the liver and raise blood sugar back to baseline, according to metabolic health expert and Levels advisor Dominic D’Agostino, PhD. All of these fight-or-flight hormones can also temporarily increase heart rate and trigger symptoms such as palpitations, tremors, and anxiety.
Now, let’s consider high blood sugar. Per D’Agostino, research suggests that hyperglycemia can prompt changes in the functioning of the autonomic nervous system—specifically, it may increase the activity of the fight-or-flight sympathetic nervous system, which elevates heart rate, and simultaneously downregulate the activity of the parasympathetic nervous system (by suppressing the vagus nerve), which essentially magnifies the increase in heart rate. In one 2022 study, people with higher fasting glucose levels had a significantly higher resting heart rate than people with normal fasting glucose—likely related to the fact that acute and chronic insulin resistance are associated with increased sympathetic activity, per the study authors.
Acute hyperglycemia in healthy people can also prolong the QTc interval—the time it takes the heart’s ventricles to contract and then recover with each beat—and, over time, this may increase the risk of cardiac arrhythmias (more on those later). Additionally, D’Agostino says the rise in insulin after a blood sugar spike triggers sodium retention, which is associated with an expansion of plasma volume that can increase blood pressure and heart rate.
Blood sugar also impacts heart rate variability (HRV), a measure of the slight variation in time between heartbeats. Higher HRV is thought to be a marker of resilience to physiological stress. In a 2022 clinical trial, participants who consumed glucose and fructose solutions experienced a swift and significant decline in HRV as blood glucose rose.
How does blood sugar affect heart rate in the long run?
While the short-lived palpitations and alterations in heart rate related to the occasional spike or dip in blood sugar aren’t usually cause for concern, we know that repeated blood glucose spikes have the potential to cause cardiovascular damage. And, once someone has prediabetes or diabetes, they are at significantly greater risk of developing a cardiac arrhythmia.
An arrhythmia is an abnormal heart rhythm, in which the heart beats too fast, too slow, or irregularly. Frequent heart palpitations could potentially be a symptom of an arrhythmia, but not always. And while some arrhythmias are harmless and simply need to be monitored, others require treatment, as they can impair blood flow from the heart to your body, damage organs, and lead to serious cardiovascular issues such as stroke, heart failure, or cardiac arrest.
A 2020 study found an overall 35 percent increased risk of atrial fibrillation (AFib)—a common type of cardiac arrhythmia in which the heart’s upper chambers beat irregularly—among people with Type 2 diabetes compared to healthy controls. Risk was highest among diabetes patients with poorer glycemic control and kidney disease, but risk was still significant among diabetes patients with good glycemic control. Other studies reveal similar findings, with a 2018 review showing a 20 and 28 percent increased risk of AFib among people with prediabetes and diabetes, respectively. This review also revealed a dose-dependent relationship—for every 20 mg/dL increase in blood glucose, risk of AFib increased by 11 percent.
While there’s a clear association between diabetes and arrhythmias, this complex relationship is not fully understood. Researchers.) and heart health experts speculate that several mechanisms are at play. For example, consistently elevated blood glucose levels can contribute to the development of advanced glycation end products (AGEs), harmful compounds formed when excess glucose in the blood sticks to proteins and fats. When these AGEs interact with our tissues, they can trigger inflammation, oxidative stress, and, ultimately, organ damage and fibrosis that interferes with the normal electrical conduction of the heart. Diabetes can also contribute to autonomic nervous system dysfunction (including autonomic neuropathy) and mitochondrial dysfunction, which can promote oxidative stress and alter cardiac cell function. Additionally, diabetes can contribute to high blood pressure, which is a major risk factor for AFib.
In addition to cardiac arrhythmias, uncontrolled blood sugar can harm cardiovascular health in other ways. Namely, it can promote atherosclerosis (arterial plaque buildup that puts you at risk for heart attack and stroke) by raising LDL cholesterol and triglycerides, lowering HDL cholesterol, and promoting inflammation and blood vessel damage.
What can you do for optimal blood sugar and heart health?
In the short term, blood glucose spikes and dips may contribute to an elevated heart rate or temporary palpitations. And while these palpitations may not be an immediate cause for concern, consider them motivation to take additional steps to stabilize your glucose.
- Craft your meals and snacks with primarily whole foods, and always pair carbs with a source of fiber, protein, and healthy fat for a more gradual rise and fall in blood sugar.
- Take a brisk walk after meals to improve glucose control and cardiovascular health. Aim for a 30-minute walk shortly after meals, and if that’s not possible, try to squeeze in 2-minute micro walks every 30 minutes or so throughout the day.
- Learn about your individual carb response using a continuous glucose monitor (CGM). “Monitoring your glucose response to a meal is essential in understanding how food impacts glucose stability, heart rate, and blood pressure,” D’Agostino says. “Knowing your carbohydrate threshold and ensuring that you have sufficient protein and fiber will go a long way in optimizing these important cardiometabolic biomarkers.”
- Be mindful of trends in your resting heart rate, but don’t overanalyze every additional beat! A slight increase after eating is normal—regardless of what you eat—due to the increased cardiac output required to support digestive processes. “This could result in a 5 to 20 percent increase in heart rate, depending upon the person and size of the meal,” D’Agostino says. To put this in perspective, If your typical daytime resting heart rate is around 75 bpm, this might bump you up somewhere between 79 to 90 bpm.
- Use this guide to talk to your doctor about blood sugar, which includes suggestions on what blood tests to ask for to help monitor your metabolic health.
In the long run, keeping glucose in check is a must if you want a healthy cardiovascular system.
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