What factors affect blood glucose levels?

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Samantha Markovitz, NBC-HWC

At first glance, identifying what factors affect blood glucose levels can seem like a fairly simple exercise: When carbohydrates are consumed, blood sugar goes up. When insulin is injected, blood glucose goes down.

However, as someone living with type 1 diabetes (T1D), you know it's not always so clear-cut!

Despite your best efforts to manage the disease, blood glucose levels can fluctuate. These swings are often caused by factors that are outside of your control — and can result from decisions unrelated to your diabetes.

If you've been left wondering why your blood sugar is high or low after you took what you thought was the "right" action, it's important to consider the many unique factors that affect your levels. Here are some common (yet frequently overlooked) reasons you may be struggling with your diabetes management.

Time of day

For starters, take a look at the clock. According to the Cleveland Clinic, many people living with T1D experience high blood sugar in the morning. There are two potential causes of hyperglycemia at this time of day, the source reports. They include the dawn phenomenon and the Somogyi effect.

The dawn phenomenon sees individuals' blood glucose levels rise in the morning, as the body prepares to begin the day, due to the release of stored glucose and hormones that reduce sensitivity to insulin. The Somogyi effect also results in high blood sugar upon waking, as the liver instinctively releases counterregulatory hormones to boost glucose levels into a safe zone when they dip overnight.

Thankfully, you can plan ahead for these situations. Insulin doses can be adjusted to mitigate the spike that occurs from the dawn phenomenon and prevent overnight lows that lead to the Somogyi effect. Insulin pump therapy can also be beneficial — these devices and related supplies allow you to mimic the pancreas' functions and make adjustments with various basals, even while sleeping.

Food combinations

Eating for balanced blood glucose isn't just about what you eat but also the composition of the meal. Foods that are heavy in carbohydrates and low in other macronutrients can cause a quick spike in blood sugar, while those that are high in fat or protein can cause a delayed spike. To learn about the way your body typically reacts to different combinations of carbs, fats, proteins and fiber, it helps to experiment. By checking in with yourself, you'll be better equipped to address — and avoid — future issues.

For instance, pairing a carbohydrate-containing food (like a bowl of berries) with food that contains healthy fats and protein (like Greek yogurt or cottage cheese) can help prevent a blood sugar spike that might normally occur when eating the berries alone. This is because the fat and protein help to slow down the rate of absorption.

As careful as you may be, it's always good to be prepared. The American Diabetes Association notes that meals high in fat or protein may need to be accounted for with insulin to prevent a delayed spike, so it's best to consult with your diabetes team about your diet.

Physical activity

Exercise is an important part of living a healthy life with T1D, but it's not a one-size-fits-all activity. As you may already know, the effect on your blood glucose levels can vary depending on the type of exercise.

For example, aerobic activities like running typically cause blood glucose to drop, but anaerobic activities like weight training can cause a spike. Meanwhile, hybrid exercise routines can cause your blood sugar to trend in either direction. Yard work, a day of shopping and moments of intimacy are all physical activities that can also cause a variation in your blood glucose.

As you do with your insulin doses, adjusting the time of day you exercise is a smart choice. You can decide if you're a morning go-getter or an afternoon powerhouse based on your personal experiences and what works best for you. Just remember to plan ahead for potential lows and highs. You may also want to consider using a continuous glucose monitor (CGM) that enables to you track blood sugar levels and spot trends during your workouts.


Did you know that certain types of non-diabetes medications can affect blood glucose levels? It's true.

While it's commonly known that steroidal treatments can cause hyperglycemia, some drugs that fight infection can also cause drug-induced hypoglycemia, according to MedlinePlus. There are many prescription and over-the-counter drugs (including supplements) that can have unanticipated effects on blood glucose, so it's important to stay aware of potential conflicts.

When being prescribed a medication, ask the physician, your endocrinologist, your certified diabetes educator and your pharmacist about how new medications may impact your blood sugars. If you notice a change when you switch medications or start something new, reach out to your medical team for guidance.

Caffeine intake

Caffeine affects everyone differently, so it's important for individuals with T1D to understand how their bodies react. For instance, you may find that drinks containing caffeine cause a spike in your blood glucose.

The Mayo Clinic indicates that consuming one to two 8-ounce cups of coffee may cause fluctuations in blood sugar, so try monitoring your body's reaction to caffeine. You can also experiment with different add-ins, like non-dairy milk vs. cow's milk, to see if that helps. Some people find that they need to take insulin when drinking black coffee — so work with your diabetes care team to figure out what works best for you.


When the body undergoes physical or emotional stress, blood glucose levels can react erratically. Typically, people find that stress raises blood sugar, but it is possible to see dips as a result of stress as well. The University of California San Francisco explains that epinephrine (adrenaline), glucagon, growth hormone and cortisol are all part of the body's stress reaction, resulting in blood glucose variability.

Daily life is full of stressors and living with a chronic condition can be an additional source of stress. Finding ways to manage your stress and cope with T1D in a healthy way is key.

Ultimately, living with type 1 diabetes requires preparation, flexibility and the ability to improvise. Knowing what factors affect blood glucose levels can help you effectively manage your symptoms and live a full, healthy life.

Interested in researching CGMs, diabetes management devices and testing supplies available? Visit the Edgepark website to peruse the many products offered as well as more information and insights relating to diabetes.

Samantha Markovitz, NBC-HWC

Bio: Samantha Markovitz, NBC-HWC is a Mayo Clinic-trained National Board Certified Health and Wellness Coach and the author of “Type 1 Diabetes Caregiver Confidence: A Guide for Caregivers of Children Living with Type 1 Diabetes.” Drawing from her own experience in living with T1D, Samantha is dedicated to empowering individuals and families to live well and thrive while managing health challenges and achieving their goals.

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