For people living with type 1 or type 2 diabetes, one of the major goals is targeting near-normal blood glucose levels over the long-term. Studies have shown that prolonged elevated blood sugar is the major risk factor for developing complications of diabetes, while avoiding high blood glucose levels dramatically lowers the risks of complications.
Some people living with diabetes may be aware of their blood sugars on a day-to-day basis because they are using devices such as a blood glucose meter or continuous glucose monitor. Others may only be aware of their average blood sugar levels every few months when they have blood work done for their appointment with the healthcare team. With either method, I commonly see fluctuations in blood glucose levels over time and it is helpful for me to review with my patients which factors could be contributing to these changes.
Although there are many factors that can affect blood glucose levels, I usually think of 5 major categories.
1. Food
Blood sugar levels are affected by when you eat, how much you eat and the type of food you eat. We expect blood glucose levels to rise soon after eating and take up to 2 hours to return to baseline levels. Low glycemic index foods do not result in as much of a glucose spike as high glycemic index foods. Some foods that are high in both carbohydrates and fats (pizza is a good example) can lead to blood sugar levels being elevated after eating for a longer period of time.
2. Physical activity
Physical activity is beneficial for diabetes and general health, and at least 150 minutes of moderate-to-vigorous physical activity each week is recommended for people with diabetes. Most exercises that cause you to breathe harder, perspire or increase your heart rate will lower blood sugar levels; examples of these include brisk walking, running or swimming. On the other hand, resistance exercises, which focus on building muscle strength, can temporarily increase blood sugar levels.
I commonly see seasonal changes in blood sugar levels as a result of corresponding changes in physical activity. In the winter, people tend to stay indoors and be less physically active, and this can result in higher blood sugar levels. It is important to find strategies to maintain physical activity consistently, even in poor weather. For example, walking briskly inside a shopping mall can be a good option.
3. Medications
You may be prescribed medications for diabetes to lower your blood glucose levels. Taking these medications exactly as prescribed by your healthcare team will help you maintain lower blood sugars.
Some medications that are prescribed for other health conditions can also affect blood glucose levels. For example, steroid pills such as prednisone raise blood sugars substantially.
4. Other illnesses
When someone who has diabetes is sick for another reason, it is common to see changes in blood glucose levels. Having an infection (for example, COVID-19 or influenza) can often lead to higher blood sugar levels due to higher levels of stress hormones during this time. If someone is not drinking much and becomes dehydrated, this can also lead to higher blood glucose levels. On the other hand, if someone is eating much less than usual because their appetite is low or they are experiencing nausea or vomiting, then blood glucose levels could be lower.
5. Stress
As mentioned above, higher levels of stress hormones increase blood sugar. One of the key stress hormones is cortisol, and this hormone is at its highest levels in the early morning. Some people with diabetes notice a blood sugar spike in the early morning as a result of this cortisol surge, and this effect is referred to as the ‘dawn phenomenon’. Emotional stress may also lead to higher blood glucose – both through raising stress hormones and through the behavioural impacts of stress, such as doing less physical activity or making less healthy food choices.
As you can see, there are many factors that affect blood glucose levels. When considering your blood sugars, and particularly if there are fluctuations or changes over time, it is helpful to think about the impact of food, physical activity, medications, illnesses and stress.
