Glucose (blood sugar)

What is glucose?

Glucose is a simple sugar that your body uses as its primary energy source. Every cell, from the brain to the muscles, needs glucose to function. Your body obtains glucose from the carbohydrates in your diet: bread, fruit, vegetables, and dairy products all contribute.

After a meal, the glucose concentration in the blood rises. The pancreas responds to this by producing insulin. Insulin acts like a key: it opens the cells so that glucose can flow in and be converted into energy. The body stores what is not immediately used as glycogen in the liver and muscles.

The glucose level in the blood is expressed in mmol/L, which stands for millimoles per liter. A healthy fasting value is usually between 4.0 and 6.0 mmol/L.

What does a glucose test measure?

A blood test for glucose provides a snapshot of the sugar concentration in your blood at the moment of collection. The test is usually performed on an empty stomach, meaning after at least eight hours without food or drink (except water). This ensures the result is not influenced by a recent meal and the value is easily comparable to reference values.

The test provides insight into how your body handles blood sugar regulation. In the event of a single elevated value, the measurement is usually repeated on another day to obtain a reliable result. In addition to the fasting glucose measurement, there is also the glucose tolerance test, in which you drink a sugary drink followed by multiple blood draws.

What do abnormal values ​​mean?

Glucose levels that are too high

A fasting glucose value of 7.0 mmol/L or higher, measured at two separate times, may indicate diabetes mellitus. In diabetes, insulin production is insufficient or the body responds poorly to it, causing glucose to accumulate in the blood instead of flowing into the cells.

Besides diabetes, other factors can also increase glucose levels. Serious infections, a heart attack, or disorders of the adrenal or pituitary gland can disrupt energy metabolism and temporarily cause elevated blood sugar. Certain medications, such as corticosteroids, and conditions of the pancreas or liver can also play a role.

Symptoms that may be consistent with high blood sugar include: persistent thirst, frequent urination, unwanted weight loss, fatigue, blurred vision, tingling in the hands or feet, and wounds that are difficult to heal.

Low glucose levels

A value below 4.0 mmol/L is considered too low. This rarely occurs in healthy people but can happen during prolonged fasting or a severely low-calorie diet. In people with diabetes, low blood sugar sometimes develops when they have used more blood sugar-lowering medication than necessary, or when they have been physically active without eating enough.

Symptoms of low glucose levels may include: dizziness, trembling, headache, feelings of hunger, confusion, a rapid heartbeat, or, in severe cases, fainting. The body signals this quickly because the brain is highly dependent on a constant supply of glucose.

When is measuring useful?

A glucose measurement is useful if you have symptoms that may be consistent with impaired blood sugar regulation. However, even without symptoms, measuring can be helpful if you have multiple risk factors for developing type 2 diabetes.

Factors that increase the risk include: being overweight, lack of physical activity, being over 45, a family history of diabetes, high blood pressure, or a previous heart or vascular problem. Women who had gestational diabetes during a previous pregnancy are also at increased risk.

During pregnancy, a glucose tolerance test is recommended around weeks 28 to 29. This is the period in which gestational diabetes occurs most frequently. Early detection is important because high blood sugar during pregnancy poses risks for both mother and child.

Having your glucose levels checked regularly gives you insight into your metabolic health and offers the opportunity to take timely action if the values ​​fall outside the normal range.