When blood glucose levels run high, people often assume it must be related to food choices, missed medication, or lack of exercise. While these are common causes, there are many other factors that can influence blood glucose levels.

Diabetes education programs emphasise that glucose levels are affected by a range of everyday factors including hormones, stress, illness, sleep, and hydration. This is why people sometimes see higher readings even when they feel they have done everything “right”. Understanding these less obvious influences can help explain unexpected glucose readings and support better diabetes management.

Below are five less common reasons your glucose levels may be higher than expected.

1. Stress and emotional pressure

Stress can have a significant impact on blood glucose levels. When the body experiences stress, whether emotional, physical, or psychological, it releases hormones such as cortisol and adrenaline.  These hormones trigger the liver to release stored glucose into the bloodstream as part of the body’s natural “fight or flight” response. While this response is helpful in emergency situations, it can raise blood glucose levels in people living with diabetes.

Stress may come from many sources including work pressures, family responsibilities, illness, financial concerns, or even the ongoing demands of managing diabetes itself. Developing strategies to manage stress may help reduce this effect. Activities such as walking, meditation, breathing exercises, or spending time outdoors may help lower stress levels and support overall wellbeing.

Recognising the relationship between stress and glucose levels can also make unexpected readings feel less confusing or discouraging.

2. Poor sleep

Sleep plays an important role in regulating hormones that influence glucose metabolism. When sleep is disrupted or shortened, the body may become more resistant to insulin. This means glucose remains in the bloodstream for longer rather than moving into the cells where it is used for energy.  Sleep deprivation may also increase hunger hormones, making people more likely to feel hungry and crave high-energy foods.

Many adults benefit from seven to nine hours of sleep each night. Maintaining consistent sleep routines, limiting screen exposure before bedtime, and creating a comfortable sleep environment may help improve sleep quality. If poor sleep is ongoing, discussing this with a healthcare professional may be helpful as sleep quality can significantly influence diabetes management.

3. Dehydration

Hydration is another factor that can affect glucose levels but is often overlooked. When the body becomes dehydrated, the amount of fluid in the bloodstream decreases. This can lead to a higher concentration of glucose in the blood.

High glucose levels themselves can also increase urination, which may further contribute to dehydration. This creates a cycle where dehydration and elevated glucose levels reinforce each other.  Drinking water regularly throughout the day can help support hydration and overall body function. Maintaining adequate fluid intake may be especially important during hot weather, illness, or increased physical activity.

4. Hormonal changes and the dawn phenomenon

Some people notice their glucose levels rise in the early morning even though they have not eaten overnight. This pattern is known as the dawn phenomenon. In the early morning hours, the body releases hormones such as cortisol and growth hormones to prepare for waking. These hormones stimulate the liver to release glucose into the bloodstream.

In people without diabetes, the body typically produces additional insulin to balance this effect. However, in people with diabetes this response may not occur, leading to higher morning glucose levels. Hormonal changes during puberty, menstrual cycles, pregnancy, or ageing can also influence insulin sensitivity and glucose patterns.

Identifying patterns in glucose readings may help determine whether hormonal changes are contributing to higher levels. 

5. Illness or infection

When the body is fighting illness or infection, glucose levels may increase even if a person is eating less than usual. During illness the body releases stress hormones that increase glucose production to provide energy for the immune system. As a result, glucose levels may rise despite reduced food intake.

When you are living with diabetes, monitoring glucose levels more frequently during illness can help identify changes early. Staying hydrated and following individual sick-day management plans may help manage glucose during these periods. If glucose levels remain very high or symptoms worsen, medical advice should be sought.

Blood glucose levels are influenced by far more than food alone. Stress, sleep, hydration, hormones, illness, medications, and daily routines can all affect how the body regulates glucose. Recognising these factors can help people understand unexpected readings and make informed decisions about their diabetes management.

Monitoring patterns over time and discussing concerns with healthcare professionals such as doctors, diabetes educators, or dietitians can help identify underlying causes and guide appropriate adjustments. Understanding the many factors that influence glucose levels can make diabetes management feel less frustrating and help you respond more confidently when their readings change.

By Robbie Tyson, Credentialled Diabetes Educator