Quick version
Diabetes is one of our most common chronic diseases and involves an impaired ability to regulate blood sugar. Elevated blood sugar levels can occur both temporarily and long-term, but it is the long-term impact that increases the risk of complications.
- Diabetes affects approximately 500,000–600,000 people in Sweden, mainly type 2 diabetes.
- Normal blood sugar levels are kept within narrow limits in healthy people thanks to insulin.
- Diabetes can be diagnosed with fasting glucose, HbA1c or glucose load.
- High blood sugar (hyperglycemia) can occur during stress, infection, physical inactivity or inadequate treatment.
- Long-term elevated blood sugar can damage blood vessels, nerves and organs.
- Blood tests such as fasting glucose and HbA1c are central to suspicion and follow-up.
In Sweden, approximately 500,000–600,000 people live with diabetes, with the vast majority having type 2 diabetes. Type 2 diabetes is most common in adults, but the incidence is increasing at younger ages, while type 1 diabetes often debuts in childhood or adolescence. This makes diabetes one of the most common chronic diseases in the population and a significant public health issue. Measuring and interpreting blood sugar is central to diagnosis and follow-up.
Normal blood sugar levels in people without diabetes
In people without diabetes, blood sugar is kept within a relatively narrow range. This is because insulin is released quickly and effectively after a meal, which allows glucose to be absorbed into the body's cells. According to international guidelines, diabetes can be diagnosed if:
- Fasting plasma glucose ≥ 7.0 mmol/L on two separate occasions
- HbA1c ≥ 48 mmol/mol (6.5%)
- Plasma glucose ≥ 11.1 mmol/L two hours after a standardized glucose load
These threshold values are used to determine whether the body has difficulty regulating blood sugar and whether there is a need for further investigation or treatment.
What happens to blood sugar in diabetes?
In diabetes, the body's ability to regulate blood sugar is impaired. Either no insulin is produced at all (type 1 diabetes), or insulin is present but the body responds less well to its effects (type 2 diabetes). In both cases, this leads to insufficient glucose being taken up by the cells and instead remaining in the blood.
The consequence is that blood sugar levels rise, especially after meals. In untreated or inadequately treated diabetes, blood sugar levels can become very high, sometimes 15–30 mmol/L or more, especially in connection with infection, stress or other physical exertion. This condition is called hyperglycemia.
Classification of high blood sugar
Elevated blood sugar levels are often classified as follows:
- Elevated blood sugar: 10.0–13.9 mmol/L
- Significantly high blood sugar: > 13.9 mmol/L
In practice, however, it is not a single value that is decisive, but how often and for how long the blood sugar is elevated.
Temporary or prolonged high blood sugar
A temporary high blood sugar value can occur for several reasons, for example:
- a carbohydrate-rich meal
- stress, pain or lack of sleep
- reduced physical activity
- infection or fever
Such temporary increases often normalize on their own or can be corrected with treatment, for example adjusting the diet, physical activity or – in people on insulin treatment – an extra dose of fast-acting insulin. However, if the blood sugar is repeatedly too high, especially at the same time of day or after specific meals, the situation should be analyzed more carefully. There may then be a need to adjust the treatment or identify underlying factors that affect blood sugar control
Why is prolonged high blood sugar harmful?
When blood sugar is elevated for a long time, the body's tissues are affected at the cellular level. Glucose binds to proteins in the walls of blood vessels and in connective tissue, which gradually changes their structure and function.
In the long term, this can lead to:
- damage to small blood vessels, for example in the eyes, kidneys and nerves.
- damage to large blood vessels, with an increased risk of heart attack and stroke.
- nerve damage with reduced sensation, pain or numbness.
- impaired wound healing and increased susceptibility to infection.
It is these long-term changes that are behind many of the complications associated with diabetes.
Blood tests for suspected diabetes
If diabetes or impaired blood sugar regulation is suspected, certain blood tests are particularly relevant. Fasting glucose measures blood sugar levels after at least 8 hours of fasting and provides a snapshot of the body's glucose regulation. Elevated values may indicate impaired glucose tolerance or diabetes, but often need to be assessed together with other findings.
An important complementary test is HbA1c, which reflects the average blood sugar level over the past 2–3 months. Unlike fasting glucose, HbA1c is less affected by temporary variations, such as stress or a single meal, and is therefore used both for diagnosing and monitoring diabetes.
For those who want to do a more comprehensive investigation, we have developed an in-depth health check with a focus on diabetes and blood sugar regulation, where several relevant markers are analyzed together. This provides a broader picture of how the body handles glucose and can help identify early signs of insulin resistance or diabetes – even before clear symptoms have developed.
