HbA1c: your average blood sugar over three months

What HbA1c measures

HbA1c stands for glycated haemoglobin. Haemoglobin is the protein in your red blood cells that carries oxygen. When glucose circulates in your blood, part of it attaches to that haemoglobin, and the bond lasts as long as the red blood cell lives.

Because a red blood cell survives for roughly three months, the percentage of glycated haemoglobin reflects how high your blood sugar has been on average during that period. A single measurement therefore summarises months of blood sugar in one number, without you having to track anything yourself.

HbA1c or a fasting glucose?

A fasting glucose is a snapshot. That value is influenced by what you ate the evening before, how you slept, whether you are ill, how much stress you were under and whether you exercised shortly beforehand. Two measurements in the same week can therefore differ noticeably.

Even so, one value does not replace the other. Glucose shows how your body is doing right now, HbA1c shows the pattern over a longer period and is therefore less sensitive to chance. Precisely because they answer different questions, they are often requested together in one package in practice. If you first want only the moment in view, you can also have your glucose tested separately, fasting or non-fasting.

The grey zone before diabetes

Type 2 diabetes rarely develops overnight. It is almost always preceded by a period in which the body becomes less sensitive to insulin and blood sugar slowly rises. That phase, often called prediabetes, can last for years and usually causes few or no symptoms.

This is exactly where HbA1c is useful: it picks up a gradual rise that you do not feel yourself and that a single fasting glucose can miss. If your result falls in the transitional range indicated by the laboratory, that is not a diagnosis, but it is a signal worth discussing.

At this stage there is often still much to gain through diet, exercise and weight. Our doctors indicate in your report whether checking in with your GP is advisable.

Who benefits from measuring?

HbA1c is particularly relevant if you have an increased chance of dysregulated blood sugar. Think of:

• being overweight, especially fat around the abdomen
• type 2 diabetes in parents or siblings
• polycystic ovary syndrome (PCOS)
• a history of gestational diabetes
• raised blood pressure or abnormal cholesterol values
• little physical activity
• age from around 45 onwards
• long-term use of certain medication, such as corticosteroids

Symptoms that may fit with long-standing high blood sugar include excessive thirst, frequent urination, fatigue, blurred vision and wounds that heal slowly. If you recognise those, do not tackle them on your own but raise them with your GP.

When to measure again?

Because HbA1c is an average over months, the value changes slowly. Measuring again soon afterwards therefore adds little: you mainly see measurement noise rather than the effect of what you changed.

If you have adjusted your diet, weight or exercise routine, it is customary to measure again only after a few months. If your situation is stable and you are measuring mainly as a check, a wider interval is enough. What suits your case depends on your result, your risk profile and any treatment. Your doctor or GP determines that interval.

When HbA1c works less well

HbA1c is reliable as long as your red blood cells survive for a normal length of time. When that is not the case, the value can become distorted. This applies, for example:

• with anaemia
• with inherited haemoglobin disorders
• after a recent blood transfusion or substantial blood loss
• with advanced kidney disease
• during pregnancy

In those situations blood sugar is usually assessed in another way. Our doctors take this into account when reviewing your result.

At Bloodworks you have HbA1c drawn at one of the 1000+ collection points in the Netherlands, after which you receive a personal PDF report explaining your value and, where there is reason to, advising you to contact your GP.