Practical guide to interpreting blood glucose levels
Good morning! After discussing blood glucose levels and their influencing factors, it’s time to learn how to interpret your blood glucose readings. Glucose values have different meanings and relevance depending on the situation, as many factors affect them. Knowing how to interpret these levels provides valuable information about the individual. Today, various tests are available to measure blood glucose levels, with the most common being fasting blood tests and capillary glucose tests (anytime using a specific meter). These tests give us glucose levels at a specific moment and standardized average values for classification. In contrast, recent advancements in continuous glucose monitoring (CGM) technology allow us to track glucose levels over a 24-hour period and gain insights into deeper trends related to health, such as glucose variability—a measure of fluctuations in glucose throughout the day, as we do at Glucovibes.
If you want to learn more about these values and how to interpret them, keep reading:
What glucose levels are considered 'normal'?
According to the American Diabetes Association (ADA), normal fasting blood glucose levels are considered to be less than 100 mg/dL. Postprandial glucose levels are considered normal if they are less than 140 mg/dL, and glucose levels should return to pre-meal values within two hours after eating. Generally, blood glucose levels between 80-120/140 mg/dL can be considered normal, depending on the time of day. It’s important to note, as discussed in a previous post, that these values can vary significantly under different physiological conditions, such as physical exercise, which will be covered in the next section. For Continuous Glucose Monitoring (CGM), there are no standardized and universally accepted criteria for what constitutes “normal” 24-hour glucose levels. Scientists are still gathering data from healthy individuals using CGM technology to establish average values.
So, how can you maintain your blood glucose levels within these mentioned ranges? Keeping your glucose levels stable is more complex than simply following a list of “eat this, avoid that” foods. Each person has an individual response to food in terms of their glucose levels. Studies have shown that two individuals can experience different changes in glucose levels after consuming the same foods.
Glucose levels in sports practice
As previously discussed in the post on glucose and exercise, glucose levels can vary significantly during physical activity. They may range from 110 mg/dL to 180 mg/dL, and these values can be highly individual. Continuous Glucose Monitoring (CGM) can help better understand each person’s responses during exercise, make appropriate decisions related to physical activity, and evaluate the effectiveness of those decisions. It also helps in determining the need for carbohydrates as fuel for exercise; fast-acting carbohydrates should be available at all times to address imminent or real low blood sugar levels before and during activities.
In this context, glucose levels, as a metabolic response to the physiological ‘stress’ of exercise, are crucial for athletic performance. For example, it is becoming increasingly clear that to perform at a moderate-to-high intensity (RPE 8/10), certain minimum glucose levels are necessary, which metabolically represents a ‘metabolic adequacy.’ As mentioned before, this is a requirement for optimal performance.
Hyperglycemia and hypoglycemia
Hyperglycemia refers to elevated blood glucose levels, occurring when the body does not properly remove glucose from the bloodstream (entry into tissues and cells). Prolonged high glucose levels can damage blood vessels and nerves over time, potentially leading to problems in the eyes, kidneys, or heart, as well as numbness in the hands and feet. Extremely high blood glucose levels can lead to coma and, in some cases, death. Hyperglycemia is considered when fasting glucose levels exceed 100 mg/dL or postprandial levels exceed 140 mg/dL (2).
Hypoglycemia is when blood glucose drops significantly below normal levels. Generally, hypoglycemia is defined as glucose falling below 70 mg/dL. When this happens, the body may release epinephrine (adrenaline), which can cause a rapid heart rate, sweating, anxiety, blurred vision, and confusion, but also helps the body mobilize glucose in the blood. If blood glucose levels remain very low for too long, they can lead to seizures, coma, and, in very extreme cases, death.
Conclusions
In conclusion, ‘normal’ blood glucose values are considered to be between 80-120/140 mg/dL. However, as previously discussed, these levels can vary depending on the time of day or specific situation. During physical activity, values typically range from 110-180 mg/dL, and these can vary greatly between individuals. Glucose levels above 140 mg/dL are defined as hyperglycemia, while levels below 70 mg/dL are considered hypoglycemia.
Therefore, maintaining stable blood glucose levels is not easy, as each individual’s glycemic response to situations, food intake, exercise, etc., is different. How often have you heard that lower glucose levels are better for your health? However, having glucose levels that are too low can also have serious consequences for the individual. Context and individualization are key to each person’s metabolic health.
References
- [1] Rodriguez-Segade S, Rodriguez J, Camiña F, Fernández-Arean M, García-Ciudad V, Pazos-Couselo M, García-López JM, Alonso-Sampedro M, González-Quintela A, Gude F. Continuous glucose monitoring is more sensitive than HbA1c and fasting glucose in detecting dysglycaemia in a Spanish population without diabetes. Diabetes Res Clin Pract. 2018 Aug;142:100-109.
- [2] Monnier L, Colette C. Target for glycemic control: concentrating on glucose. Diabetes Care. 2009 Nov;32 Suppl 2(Suppl 2):S199-204.
- [3] Wendy Marcason, RD. Is There a Recommended Target Range for Blood Glucose for the Type 1 Diabetic Endurance Athlete?. Journal of the Academy of Nutrition and Dietetics. 2021 Aug; 112:2092.