If you’re under the weather, you may have more than just that cold to worry about. In addition to giving you symptoms like fatigue and pain, infections can increase your blood sugar. When you come down with an illness like a cold or the flu, your body leaps into action, emitting a stress response that allows it to recruit the proper immune cells and enable them to fight off the pathogen.

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Why Blood Sugar Spikes When You’re Sick

While elevated stress is necessary for your immune system to be effective, it can also result in elevated blood glucose levels. This happens for the following reasons:

Epinephrine (or adrenaline)

This is the major hormone released when your body is under stress. Epinephrine is helpful when you’re sick because it activates macrophages and cytokines, enhancing the immune response.¹ 

At the same time, epinephrine also stimulates glycogenolysis (the breakdown and release of glucose into the bloodstream) and gluconeogenesis (the creation of new glucose molecules), raising your blood sugar.²

When your blood sugar becomes high, your pancreas releases insulin in an attempt to reduce your blood glucose levels. You can think of insulin as the key that unlocks the door so that sugar molecules can be taken up into cells and out of the bloodstream. While people who are metabolically healthy can usually keep up with this increased demand for insulin, people living with type 1 diabetes or type 2 diabetes are at risk for a serious, life-threatening condition called diabetic ketoacidosis. 

Cortisol

Cortisol levels also increase during acute illnesses.³ Cortisol maintains the body’s homeostasis by balancing the immune response and downregulating inflammation. In addition to its direct role in the immune system, cortisol also causes an increase in blood sugar. Excess cortisol overtime can cause cells to become insulin resistant and may eventually lead to diabetes. 

What Infections Can Cause High Blood Sugar?

Your blood sugar may not spike every time you get sick, but severe infections like the following will likely cause an increase in your glucose levels:

• Influenza (the flu)
• Urinary Tract Infections (UTI)
• Pneumonia

<p class="pro-tip"><strong>Learn more: </strong> <a href="/blog/coffee-blood-sugar">Does Coffee Raise Blood Sugar?</a>.</p>

Other Causes of Blood Sugar Rises in Non-Diabetics

It’s normal for our blood sugar to fluctuate based on our food choices, how much we're moving, and how much stress our bodies are under. Extreme highs and lows (referred to as hyperglycemia and hypoglycemia, respectively) can negatively affect how we feel in the moment and also adversely affect our long-term health. It’s important to understand the factors that can raise your blood sugar so you can make the best lifestyle choices for yourself. 

Below are some triggers that can raise your blood sugar levels, according to the Centers for Disease Control and Prevention (CDC):⁷

Lack of sleep

When sleep-deprived, our glucose tolerance (ability to clear glucose from the bloodstream) and our insulin sensitivity (how sensitive our cells are to insulin)  decreases.⁴ Poor sleep can be the result of waking up often or not getting enough hours.

Lack of exercise

Exercise reduces our blood sugar by taking glucose molecules from the bloodstream and using them as fuel for muscle cells. In addition, both cardio and weight training exercises can make our cells more sensitive to insulin, helping to balance our blood sugar. However, our blood sugar can stay elevated for extended periods when we are sedentary. 

Stress

Hormones like epinephrine and cortisol that are released during times of stress trigger a rise in blood sugar. The body is designed to deal with intermittent stressors and can usually recover quickly, returning hormones to normal levels. Prolonged periods of chronic stress overexpose the body to cortisol and other stress hormones and can disrupt almost all your body's normal functions. This puts you at an increased risk for many health problems. 

Dehydration

Not getting enough water can also impact your glucose levels. Plasma, the liquid part of your blood, is composed of more than 90% water.⁵ When we’re dehydrated, our plasma levels can go down, increasing the sugar concentration in the blood. Think of your blood as a glass of water. If the glass is full and you pour a teaspoon of sugar in, the concentration of sugar in the water won’t be very high. On the other hand, if the glass is half full and you pour the same amount of sugar in, the concentration will be higher.

People living with diabetes are also at a higher risk of being dehydrated, especially when sick. The American Diabetes Association (ADA) suggests taking sips of sugar-free, caffeine-free drinks every 15 mins to prevent dehydration when feeling ill.⁶

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Family history

Your genes can play a role in both your glucose tolerance and insulin sensitivity.

Time of day

Blood sugar can naturally spike in the morning due to a rise in cortisol.

Caffeine

Caffeine increases the release of the epinephrine hormone, which causes the liver to release stored glucose, ultimately raising our blood sugar.

Obesity

Obesity causes excess inflammation, which negatively impacts glucose metabolism, and can lead to insulin resistance and diabetes. 

Trauma to the body

Similar to when you have an infection, when you undergo trauma like an injury, burn, or surgery, the body releases stress hormones that can increase blood glucose levels. Even gum disease, a complication for people living with diabetes, can lead to blood sugar spikes.

What are Some Side Effects of High Blood Sugar?

The best way to determine your blood sugar level and spikes is to track your levels with a Continuous Glucose Monitor (CGM). Some people don’t experience noticeable symptoms when they experience high blood sugar levels including:

• Frequent urination
• Increased thirst 
• Blurry vision
• Weight loss
• Numb or tingling feet
• Fatigue
• Yeast or other fungal infections
• Cuts and sores that take a long time to heal

How to Control Your Blood Sugar Levels When Sick

Managing your blood sugar is important to help you recover from an infection in the short term and is also crucial for your long-term health. Here are some tips on how to keep your blood sugar balanced. 

Stay hydrated

Drinking enough water can help to lower blood sugar levels. People living with diabetes often are more susceptible to dehydration and may develop serious health conditions, including diabetes mellitus. 

Water is a natural diuretic and will help the kidney flush out excess sugar. Since water does not contain fat, glucose, or carbohydrates, water is one of the best zero-calorie, low-carb drinks to consume.

Eat well-balanced meals and snacks 

Eating balanced meals by incorporating healthy fats, quality protein, and carbohydrates high in fiber (i.e., fruits and whole grains) into your diet is the best way to optimize your blood sugar levels. Try some of these ideas:

Meals

• Steel-cut oatmeal with a scoop of protein powder, berries, and nut butter
• Salad with chicken, tomato, roasted chickpeas, and avocado with olive oil dressing
• Roasted salmon with a side of quinoa and asparagus

Snacks

• Personal charcuterie - nuts, olives, almond flour crackers, cheddar cheese, and roasted turkey
• Small bowl of cottage cheese with berries
• Chia seed pudding with a scoop of chocolate protein powder 

Be aware of your medication’s ingredients

Some compounds in over-the-counter and prescription medications can raise your blood sugar. Talk to your healthcare provider or pharmacist to determine if your medications have this side effect.

Keep track of your blood sugar

Tracking your blood sugar is the best way to understand your levels clearly. CGM programs like Signos offer a way to do this conveniently and seamlessly.

Drink sugar-free liquids

While staying hydrated is essential, sugar-sweetened beverages are your blood sugar’s worst enemy. Stick to water, herbal teas, or choose sugar-free beverages.

When to See a Healthcare Professional

Your blood sugar levels can significantly affect how you feel and function, and your body is extra sensitive to blood sugar spikes and dips when you’re sick. If you notice any of the following symptoms, call a member of your healthcare team:

• Blood glucose levels above 240 mg/dL
• Blood glucose levels below 60 mg/dL 
• Fever above 101 degrees
• Excessive vomiting
• Trouble breathing
• Severe fatigue
• Excessive diarrhea

Using a CGM with Signos: Real-Time Data, Backed by AI

Signos pairs a real-time glucose biosensor with AI trained on tens of millions of data points to deliver personalized, science-backed guidance for weight management and health. See exactly how your body responds, and take action.

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<p class="pro-tip"><strong>Keep reading: </strong> <a href="/blog/watermelon-glycemic-index">Watermelon Glycemic Index: Does It Spike Blood Sugar?</a>.</p>