What raises blood sugar? 19 surprising factors besides food

Many people with diabetes or prediabetes know that sugary foods or heavy carbs can raise glucose, but there’s much more to managing blood sugar than just watching what you eat. Your environment and daily habits also play a major role in how your blood sugar behaves.

In fact, the challenges that come with our changing seasons can also influence your glucose levels in some surprising ways. Thinking about your diabetes self-care through a seasonal lens may make it easier to understand and manage these shifts.

What does a blood sugar spike feel like?

A blood sugar spike happens when glucose levels rise faster than your body can use or store it. It usually occurs after eating, but it can also happen due to stress, illness, medications, hormonal changes or other factors beyond food. And yes, you can even experience a spike if you don’t have diabetes.

When describing what a blood sugar spike feels like, for many people, it’s a mix of physical and mental symptoms. Think of it like a car—your body is revving up (or accelerating) too high and struggling to slow down.

And while everyone feels it a little differently, common blood sugar spike symptoms include:

• Feeling unusually tired or sluggish
• Sudden thirst
• Headaches
• Blurry vision
• Mood changes or irritability
• Trouble concentrating
• A rapid heartbeat
• Feeling shaky, jittery or “off”

When to talk with your doctor

If you’re noticing frequent or unexplained blood sugar spikes, even when your diet seems consistent, it’s a good idea to reach out to your doctor or diabetes care team. They can help by evaluating whether factors such as medications, stress, sleep or seasonal patterns may be contributing. In addition, they can adjust your care plan to address non-food-related triggers and monitor your glucose more closely during periods of stress, seasonal changes or lifestyle shifts.

Seasonal factors that can raise blood sugar

Because your body reacts to changes in weather, daylight, stress and routine, certain times of the year can make blood sugar management feel easier or more challenging. These seasonal shifts create patterns that aren’t always obvious at first, but once you recognize them, they can help guide your daily self-care.

With that in mind, here’s how each season can influence your blood sugar in ways that go beyond what you eat.

Winter: Cold weather, holidays and slower movement

Winter brings festive gatherings, colder temperatures and a natural tendency to slow down, which can affect your blood sugar. Illness is more common in the winter months, and both holiday stress and changes in routine can complicate glucose control.

Add in the impact of cold weather on activity levels, meal patterns and even medical devices, and winter becomes a season where blood sugar management may require a little extra attention.

1. Extreme cold. Frigid temperatures can affect your body and your diabetes supplies. Cold hands and feet, unheated storage or exposure to freezing conditions can interfere with insulin, other medications and devices like glucose monitors or insulin pumps. Even simple testing errors, such as not washing and warming your hands before a fingerstick, can lead to inaccurate readings, potentially triggering a blood sugar spike.
2. Heat sources inside the home. Direct contact with heaters, fireplaces or electric blankets can be risky if you’re living with diabetes. A study on diabetes-related admissions found that most lower-extremity burns came from intentional or accidental exposure to these heat sources. Because diabetes can reduce sensation in the skin, it may be harder to accurately judge temperature, and burns can raise glucose levels.
3. Winter viruses and colds. Seasonal illnesses, including flu, pneumonia, RSV and common colds, add extra stress to your body. People with diabetes are more vulnerable to complications from influenza, and infections can trigger the release of stress hormones that raise blood sugar. Follow up with your physician about annual flu vaccinations, as well as RSV and pneumonia vaccines, and remember to practice good hand hygiene. 

Spring: Seasonal shifts and allergy issues

Spring brings warmer weather, longer days and, unfortunately for many, an uptick in allergies. The American Academy of Allergy, Asthma & Immunology estimates that around 50 million Americans experience allergies each year. While pollen, mold, weeds and grasses don’t directly raise blood sugar, the season’s symptoms and their treatments can indirectly influence your glucose levels.

4. Steroid-containing eye and nasal treatments. Some eyedrops used to reduce itching or keep eyes moist, and certain nasal sprays designed to clear sinuses, contain steroids that may trigger a blood sugar spike.
5. Antihistamines and drowsiness. Sneezing and allergy symptoms often lead to taking antihistamines, which can cause fatigue. If this results in skipped or delayed meals, it may create low blood sugar followed by rebound spikes, disrupting overall glucose control.
6. Smoking and allergy stress. Smoking can worsen allergy symptoms and affect blood sugar. Nicotine and other chemicals reduce insulin sensitivity over time, making it harder for cells to absorb glucose efficiently, which can increase blood sugar levels.

Summer: Heat, hydration and outdoor activity

Summer brings longer days, outdoor fun and warmer temperatures, but it also introduces unique encounters that can affect your blood sugar. Older adults, in particular, are 20–30% more prone to dehydration due to reduced mobility, making hydration important, especially if you are diabetic.

7. Even mild dehydration can impair glucose regulation. One study showed that adult men with Type 2 diabetes who drank only 17–34 ounces of water per day for three days experienced a reduced glucose response. Staying well-hydrated helps prevent unnecessary blood sugar spikes.
8. Skin damage and pain act as physical stressors, triggering hormone release that can elevate blood sugar. Protecting your skin from prolonged sun exposure is key to minimizing this seasonal impact.
9. Foot blisters or infections from outdoor activity.Improper or damp footwear can cause blisters or infections, which are particularly concerning for people living with diabetes. Infections activate stress hormones, causing blood sugar to rise while the body fights off the infection. Moisture-wicking, well-fitting shoes and regular foot checks help reduce this risk.

Fall: Added stress, shorter days and changes to your routine

Autumn often brings busier schedules, approaching holidays and shorter daylight hours, all of which can contribute to what’s called “autumn anxiety.” This seasonal stress can appear as low energy, a somber mood or general unease.

Research shows that people with diabetes are two to three times more likely to experience clinical depression, and within 18 months, up to 50% of people with diabetes report diabetes distress, which is an emotional response to the daily self-care demands of managing glucose.

When the body perceives stress, it releases hormones like cortisol that prompt glucose and fat stores to be released for energy. In diabetes, insulin may not efficiently move glucose into cells, which can result in elevated blood sugar spikes. Monitoring stress and finding ways to reduce it can help keep glucose levels more stable. 

10. Lack of good, quality sleep. Sleep deprivation directly affects glucose regulation. According to the CDC, too little sleep can increase insulin resistance, make you hungrier, encourage high-carb and sugary food cravings, raise blood pressure, weaken your immune system and increase the risk of depression, anxiety and heart problems. Prioritizing consistent, restorative sleep is one of the most effective ways to prevent blood sugar spikes.
11. Too little physical activity. Regular movement improves both your mood and glucose control. Extended periods of inactivity can contribute to higher blood sugar. Incorporating moderate activity into daily routines such as walking, stretching or even standing breaks can help prevent autumn-related glucose fluctuations.
12. Missing a stress or emergency plan. Physical and emotional stressors from family conflicts or work pressures to unexpected events can trigger blood sugar spikes. Having an emergency diabetes plan or stress-management strategy in place provides peace of mind and helps your body respond more predictably during stressful moments.

Year-round factors that can raise blood sugar

For people living with diabetes, managing your blood sugar is a year-round effort. While each season brings its own unique challenges, it’s also important to recognize triggers that can affect blood sugar any time of the year.

13. Certain prescriptions can influence glucose levels, including those for high blood pressure (beta-blockers), cholesterol or triglycerides (niacin or vitamin B3), depression (antidepressants), inflammation (corticosteroids), or infections (antibiotics). Monitoring your blood sugar closely when starting or adjusting medications can help you catch changes early.
14. Hormonal fluctuations. For women, menstrual cycles can cause hormonal shifts that impact insulin sensitivity, often resulting in blood sugar spikes at predictable times of the month. Keeping track of your cycle alongside glucose readings can help you manage these changes.
15. Dawn phenomenon. Many people with diabetes experience a natural early-morning rise in blood sugar, usually between 2:00 AM and 8:00 AM. This is caused by an early-morning hormone release. Recognizing it can help you adjust your insulin or meal plan to reduce morning spikes.
16. High-altitude living or travel. Being at higher elevations can affect oxygen levels, circulation and stress on the body, sometimes leading to higher glucose readings.
17. Skipping breakfast. Missing your first meal of the day can trigger higher post-lunch glucose levels, as the body may overcompensate by releasing stored glucose. Consistent meal timing helps prevent unexpected blood sugar spikes.
18. Incorrect insulin or medication regimen. Using the wrong dose, relying on insulin that doesn’t last as long as expected or using expired insulin can all lead to elevated blood sugar.
19. Gum disease (gingivitis). Diabetes increases the sugar content in saliva, making gums more prone to infection. Gum disease triggers inflammation that can raise blood sugar.

Stay on top of your health by understanding what raises blood sugar

Don’t leave your glucose levels to chance. Understanding what raises blood sugar can help you prevent unexpected spikes and take control of your overall well-being. Stay aware of these seasonal and year-round triggers and talk with your doctor about how to manage your diabetes confidently.