The HbA1c value, also known as glycated hemoglobin or long-term blood sugar, is an important laboratory value in the diagnosis and treatment of diabetes. Unlike a single blood glucose measurement, which only provides a snapshot, the HbA1c value shows the average blood glucose level over the past 8 to 12 weeks.

The value is determined by a chemical reaction: When glucose (sugar) in the blood meets the hemoglobin in red blood cells, the two bind together. This process is called glycation. The higher the blood sugar level is over a longer period, the more hemoglobin is glycated – and the higher the HbA1c value.

Why is the HbA1c value so informative?

Red blood cells have a lifespan of approximately 120 days. The HbA1c value therefore reflects the blood sugar status of the last 2-3 months and is thus significantly more informative than a single fasting blood glucose measurement, which can be influenced by many factors such as stress, diet, or exercise the day before.

For people with diabetes, the HbA1c value is the most important measure for assessing metabolic control. It helps doctors and patients evaluate the effectiveness of therapy and make timely adjustments to avoid complications.

The classification of HbA1c values ​​helps in assessing diabetes risk and metabolic control. These values ​​are usually given as a percentage or in mmol/mol – both units describe the same value, just on different scales.

Classification of HbA1c values

Normal: An HbA1c value below 5.7% (39 mmol/mol) is considered normal and indicates that blood sugar metabolism is functioning healthily. Within this range, there is no increased risk of diabetes or its complications.

Prediabetes: Values ​​between 5.7% and 6.4% (39-47 mmol/mol) indicate impaired glucose tolerance, also known as prediabetes. At this stage, blood sugar levels are already elevated, but not yet high enough for a diagnosis of diabetes. Prediabetes is an important warning sign: Without intervention, it often develops into overt type 2 diabetes.

Diabetes: A diagnosis of diabetes mellitus is made when the HbA1c value is 6.5% (48 mmol/mol) or higher. Values ​​in this range indicate that blood sugar levels have been significantly elevated for an extended period and that treatment is necessary.

Therapy goals in diabetes

For people diagnosed with diabetes, the recommended therapeutic target is generally between 6.5% and 7.5% (48-58 mmol/mol). The exact target is determined individually with the treating physician and depends on various factors, such as age, comorbidities, and the risk of hypoglycemia.

A low HbA1c value in people with diabetes can indicate frequent episodes of low blood sugar (hypoglycemia), which can also be dangerous. Therefore, 'the lower, the better' is not always the right strategy.

An elevated HbA1c level always occurs when blood sugar levels are elevated over a prolonged period. The causes for this can be varied and range from lifestyle factors and genetic predisposition to certain diseases.

Main cause: Insulin resistance and type 2 diabetes

The most common cause of an elevated HbA1c level is insulin resistance, which leads to the development of type 2 diabetes. In insulin resistance, the body's cells no longer respond adequately to the hormone insulin, which normally ensures that glucose is absorbed from the blood into the cells. The pancreas initially produces more insulin to compensate, but eventually it can no longer keep up – blood sugar levels rise permanently.

Lifestyle factors

Unhealthy diet: A diet rich in refined carbohydrates, sugar, and saturated fats leads to frequent blood sugar spikes and promotes the development of insulin resistance. Fast food, soft drinks, and highly processed foods are typical culprits.

Lack of exercise: Physical inactivity is one of the most important risk factors for type 2 diabetes. Regular exercise improves the insulin sensitivity of cells and helps regulate blood sugar.

Obesity: Abdominal fat (visceral fat) in particular produces pro-inflammatory messengers that promote insulin resistance. A BMI over 25 and an increased waist circumference are important risk factors.

Other causes

Stress, lack of sleep, certain medications (e.g., cortisone), and hormonal disorders (e.g., hyperthyroidism, Cushing's syndrome) can also raise blood sugar levels and thus the HbA1c value. In type 1 diabetes, an autoimmune disease, the immune system destroys the insulin-producing cells in the pancreas, so that little or no insulin is produced.

An elevated HbA1c value often causes no direct symptoms for a long time, which is why diabetes is frequently detected late. The gradual development makes the disease particularly insidious, as high blood sugar can already be damaging blood vessels and organs during the symptom-free phase.

Early signs of high blood sugar

If blood sugar is significantly elevated, the following symptoms may occur:

Frequent urination: Above a certain blood sugar level, the kidneys are overwhelmed and excrete sugar in the urine. This leads to increased urination, especially at night.

Excessive thirst: Due to fluid loss, a pronounced feeling of thirst develops.

Tiredness and fatigue: When cells can’t absorb enough glucose, they lack energy—this results in tiredness, trouble concentrating, and reduced performance.

Weight loss: Despite normal or increased food intake, unexplained weight loss can occur because the body can’t properly utilize energy from food.

Blurred vision: Blood sugar fluctuations can temporarily impair vision.

Long-term consequences

If an elevated HbA1c remains untreated for years, it can lead to serious complications:

Cardiovascular disease: Diabetes is a major risk factor for heart attack, stroke, and peripheral arterial disease (circulatory problems in the legs).

Kidney damage (nephropathy): Persistently high blood sugar damages the tiny blood vessels in the kidneys and can lead to kidney failure.

Nerve damage (neuropathy): Damaged nerves can cause numbness, tingling, pain, or sensory disturbances, especially in the feet and hands.

Eye damage (retinopathy): Diabetes is one of the leading causes of blindness in adults.

Diabetic foot syndrome: Due to the combination of nerve damage and poor circulation, wounds on the feet heal poorly and can lead to serious infections.

The HbA1c test is a simple blood test usually performed by your primary care doctor or a diabetes specialist. The test requires a small blood sample, which can be taken either from a vein or as capillary blood from your fingertip.

Procedure at the doctor's office

At the doctor's visit, blood is usually drawn from a vein in your arm. The blood is then sent to a lab, where the amount of glycated hemoglobin is measured. Results are usually available within a few days. A major advantage of the HbA1c test is that you do not need to fast—the measurement can be done at any time of day and is not affected by your last meal.

HbA1c self-test for home use

There are now HbA1c self-tests that you can conveniently perform at home. These tests use capillary blood from your fingertip. After collecting the sample, you send the blood in a prepared kit to a certified lab. Within a few days, you'll receive your results digitally—often with detailed explanations and recommendations.

Home tests offer several advantages: you save yourself a doctor’s appointment, can perform the test discreetly, and have the ability to regularly monitor your HbA1c level. The accuracy of home tests meets the standards of medical laboratories.

How often should the HbA1c level be measured?

For people without diabetes, a measurement every 3 years is recommended as a preventive measure; for those at increased risk (e.g., overweight, family history), annually. People with well-controlled diabetes should have their levels checked every 3-6 months, and more frequently if there are changes in therapy or poor control.

Diet plays a central role in regulating blood sugar and therefore also HbA1c levels. Targeted dietary changes can often significantly lower your long-term blood sugar – sometimes even without medication.

Choose carbohydrates wisely

Not all carbohydrates are created equal. While simple carbohydrates (white bread, sweets, soft drinks) cause blood sugar to rise rapidly, complex carbohydrates ensure a slower, more even rise.

Recommended: Whole grain products, oatmeal, quinoa, legumes, vegetables. These foods contain fiber, which slows down sugar absorption and keeps you feeling full longer.

To be avoided: white flour products, sugary drinks, sweets, fast food, fruit juices (even 100% juice contains a lot of sugar).

Pay attention to the glycemic index

The glycemic index (GI) indicates how quickly a food raises blood sugar levels. Foods with a low GI (below 55) are particularly suitable for diabetics and people with prediabetes. Examples include most vegetables, legumes, nuts, and whole grain products.

More healthy fats, fewer saturated fats

Healthy fats from olive oil, avocados, nuts, and oily fish (salmon, mackerel) improve insulin sensitivity. Saturated fats from red meat, butter, and highly processed foods should be reduced.

Protein-rich diet

Protein has only a minor impact on blood sugar and provides a long-lasting feeling of satiety. Good sources of protein include lean meat, fish, eggs, legumes, tofu, and low-fat quark.

Regular meals

Three balanced main meals without constant snacking help to avoid blood sugar spikes. Long breaks between meals give the body time to lower insulin levels.

Besides diet, regular exercise and weight loss are the most effective ways to lower HbA1c levels. Sports and physical activity improve insulin sensitivity and help regulate blood sugar – often even with moderate activity.

Why exercise is so important

When you exercise, your muscles use glucose for energy. This immediately lowers your blood sugar. At the same time, your cells become more sensitive to insulin – they can absorb glucose better, even with less insulin. This effect lasts for hours after training.

Studies show that just 150 minutes of moderate activity per week (e.g. brisk walking, cycling, swimming) can lower HbA1c by 0.5-0.7%. That may sound small, but it can make the difference between prediabetes and normal levels.

The best sports for diabetes

Endurance sports: Walking, jogging, cycling, swimming, and dancing are ideal for improving insulin sensitivity and burning calories. Just 30 minutes a day can make a big difference.

Strength training: Building muscle is especially important, as muscles use glucose even at rest. Two to three strength training sessions per week are optimal.

Everyday movement: Taking the stairs instead of the elevator, biking instead of driving, a walk after meals—all these small activities add up and help lower blood sugar.

Weight loss as a game changer

Being overweight, especially abdominal fat, is the most important risk factor for insulin resistance. Studies show that even a weight loss of 5-10% of body weight can significantly lower HbA1c levels. In some cases, type 2 diabetes can even go into remission through weight loss—meaning blood sugar normalizes without medication.

The combination of a healthy diet and regular exercise is the most effective way to lose weight. Crash diets, on the other hand, are not recommended, as they often lead to the yo-yo effect. Focus on a long-term, sustainable lifestyle change.

If lifestyle changes alone are not enough to bring your HbA1c into the target range, medication may become necessary. Modern diabetes medicine today offers a wide variety of drugs that help lower blood sugar in different ways.

Metformin: The first-line treatment

Metformin is the most commonly prescribed medication for type 2 diabetes. It reduces glucose production in the liver, improves insulin sensitivity, and can help with weight loss. Metformin has a good safety profile and does not cause hypoglycemia. The most common side effect is initial gastrointestinal discomfort, which usually improves after a few weeks.

Other medication groups

SGLT-2 inhibitors: These medications cause excess sugar to be excreted through the kidneys. They not only lower blood sugar but also have positive effects on the heart and kidneys.

GLP-1 agonists: These drugs mimic the action of the body’s own GLP-1 hormone, which is released after meals. They lower blood sugar, reduce appetite, and promote weight loss. Well-known examples include Ozempic and Wegovy.

DPP-4 inhibitors: These tablets enhance the effect of the body’s own blood sugar-regulating hormones.

Sulfonylureas: They stimulate the pancreas to produce more insulin. Advantage: rapid action. Disadvantage: risk of hypoglycemia and weight gain.

Insulin therapy

For advanced type 2 diabetes or type 1 diabetes, insulin therapy is indispensable. Modern insulins and insulin pumps now allow for flexible and safe treatment. Fear of insulin is often unfounded—it is a life-saving medication that, when used correctly, significantly improves quality of life.

Individualized therapy

Which medication or combination is right depends on many factors: age, comorbidities, weight, kidney function, and individual goals. Your doctor will work with you to find the right therapy and adjust it regularly.

The good news: Type 2 diabetes is preventable in many cases. Studies show that consistent lifestyle changes can reduce the risk of developing diabetes by up to 60% – even in people at high risk or with prediabetes.

The most important preventive measures

Maintaining a healthy weight: A BMI between 18.5 and 24.9 is ideal. Those who are already overweight will benefit from even moderate weight loss.

Regular exercise: At least 150 minutes of moderate exercise per week, ideally combined with strength training. Every step counts – even everyday activity makes a difference.

Mediterranean diet: This diet, rich in vegetables, whole grains, legumes, olive oil, fish and nuts, is scientifically well-researched and has been proven effective in diabetes prevention.

Reduce sugar and refined carbohydrates: Soft drinks, sweets and white flour products should remain the exception, not the rule.

Sufficient sleep: 7-8 hours of sleep per night are important for a healthy metabolism. Lack of sleep increases insulin resistance.

Reduce stress: Chronic stress increases cortisol levels, which promotes insulin resistance. Relaxation techniques such as meditation, yoga, or breathing exercises can help.

Don't smoke: Smoking increases the risk of diabetes by about 40% and significantly worsens the prognosis for those with existing diabetes.

Regular check-ups

Have your HbA1c level checked regularly, especially if you have risk factors (overweight, family history, high blood pressure, elevated blood lipids). The earlier a blood sugar metabolism disorder is detected, the better the chances of counteracting it through lifestyle changes.

A diagnosis of diabetes or prediabetes doesn't mean your quality of life has to suffer. With the right knowledge, a positive attitude, and a few practical strategies, you can lead a fulfilling, active life despite the condition.

Blood sugar management in everyday life

Meal planning: Prepare healthy meals in advance so you're not tempted to reach for unhealthy convenience foods. Meal prep on the weekend can make the week much easier.

Choose snacks wisely: Always have healthy snacks on hand: nuts, vegetable sticks with hummus, cheese cubes, or hard-boiled eggs. This will help you avoid cravings and blood sugar fluctuations.

Pay attention to portion sizes: Use smaller plates to automatically eat less. Listen to your body's signals of fullness and don't eat out of habit or boredom.

Eating out with diabetes

Eating out at restaurants is no problem if you follow a few rules: Choose grilled or steamed food instead of fried. Ask for a salad or vegetables as a side dish instead of fries. Drink water or unsweetened beverages. Share dessert or skip it altogether – you're often full after the main course anyway.

Maintaining motivation

Set realistic goals and celebrate small successes. A lower HbA1c level, a lost kilogram, a week without soft drinks – these are all achievements you can be proud of. Seek support: diabetes support groups, online communities, or a supportive friend can help during difficult times.

Dealing with setbacks

It's normal for things not to always go perfectly. A slightly elevated blood sugar level after a party, a missed workout, or a week with a less-than-healthy diet are no reason to panic. What's important is that you stick with it in the long run and don't give up at the first sign of trouble. Diabetes management is a marathon, not a sprint.