eAG (estimated average glucose)

What is eAG (estimated average glucose)?

Glucose in your blood sticks slowly and irreversibly to the haemoglobin in your red blood cells. The higher your blood sugar is on average, the larger the share of haemoglobin carrying a sugar group, and that share is the HbA1c. A red blood cell lasts about four months, so the HbA1c summarises the blood sugar of the past two to three months, with the last weeks weighted most heavily. The eAG, estimated average glucose in full, is that HbA1c converted to the average glucose that goes with it. The conversion comes from a study in which more than five hundred people took thousands of glucose readings over three months, after which the average glucose was set against the HbA1c: average glucose in mg/dL is 28.7 times the HbA1c in percent minus 46.7, and that relationship was the same for men and women, young and old, with and without diabetes. In the Netherlands the HbA1c is in mmol/mol and glucose in mmol/L; that is the same conversion in other units. Your report usually does not print the eAG; you calculate it with the calculator on this page, from your HbA1c. The result is in mmol/L, the same unit as a glucose meter. Normal is an eAG below 7 mmol/L, which belongs with an HbA1c below 42 mmol/mol; from 48 mmol/mol, an eAG around 7.7, there is diabetes.

Why is eAG (estimated average glucose) relevant?

The eAG makes your HbA1c readable. Anyone who tests at home or wears a sensor knows blood sugars in mmol/L; the HbA1c is in mmol/mol and is therefore hard to set beside those numbers. The conversion removes that hurdle: an HbA1c of 53 mmol/mol becomes an average blood sugar of about 8.6, and everyone who has ever used a meter understands that number. The second reason is that an average over months is more honest than a moment. A fasting glucose is one morning and moves with sleep, stress and an infection; the eAG averages out all those mornings and afternoons and evenings. Anyone who has changed their diet, weight or exercise sees the real effect in the eAG after two to three months, independent of the day of the draw. The honest limitation is that the eAG adds nothing to the HbA1c and inherits all its limitations. The HbA1c measurement may deviate by seven percent, and that margin carries through into the conversion. Everything that changes the lifespan of red blood cells, anaemia, blood loss, a shortened survival through a blood disorder, shifts the HbA1c and so the eAG without the blood sugar having moved. And an average says nothing about the peaks and troughs beneath it: two people with the same eAG can have had a very different day.

How eAG (estimated average glucose) is worked out

The eAG has no band of its own, because it is not a test but a conversion of your HbA1c. Healthy is an eAG below 7 mmol/L, which belongs with an HbA1c below 42 mmol/mol; from an HbA1c of 48 mmol/mol, an eAG around 7.7, there is diabetes. What you may expect of the eAG depends entirely on the HbA1c beneath it, including the seven percent deviation its measurement may have.

eAG (estimated average glucose) high or low: what it means

A low eAG is favourable and means your blood sugar was low on average over the past months. Usually that comes from a falling HbA1c, so from less sugar, losing weight, more exercise or better-controlled diabetes, and that is the intention. Sometimes it is a distortion: a shorter lifespan of red blood cells, after blood loss, with a blood disorder or during recovery from anaemia, gives the cells less time to pick up sugar and pushes the HbA1c falsely down. In someone with diabetes who uses insulin, a low eAG can also mean there are too many low values beneath the average. A high eAG means your blood sugar was high on average. Usually it is the first and rarely the last: a rising HbA1c, through more sugar and fast carbohydrates, weight gain, less exercise, lack of sleep or diabetes slipping out of control; the margin on the HbA1c measurement, which can put the result seven percent up or down; and rarely a difference in how quickly someone's haemoglobin binds sugar, so the same blood sugar gives one person a higher HbA1c than another. Iron deficiency lengthens the lifespan of red blood cells and lifts the HbA1c in the same way. What you do about it: exactly what brings the HbA1c down. Cut soft drinks, fruit juice and sweets, replace white bread, white rice and biscuits with whole grains, legumes and vegetables, and eat protein and fibre with every meal, because those curb the sugar peak. Exercise daily, with strength training as well, because muscles take up glucose. Lose weight if you carry belly fat. Count on two to three months before the eAG shows it, because that is how long it takes for the red blood cells to be renewed. If the HbA1c sits in the diabetes zone, a treatment plan belongs with it. The eAG belongs beside the HbA1c it comes from, because it is the same number in a different unit, beside your fasting glucose, which shows the moment where the eAG gives the average, beside your haemoglobin and ferritin, because anaemia and iron deficiency distort the HbA1c, and beside your own meter readings or sensor, which show the peaks and troughs that disappear in an average.

How does an eAG (estimated average glucose) blood test work?

Referral

Not needed, and there is no separate request. The eAG follows from your HbA1c; you calculate it with the calculator on this page.

Fasting

Not needed. That is the advantage of the HbA1c the eAG follows from: the test can be done at any time of day, and what you ate that morning changes nothing about it.

When

When you want to know how your blood sugar was on average over the past two to three months, and not just after heavy blood loss or a blood transfusion, because then the average is wrong.

The draw

No extra tube. The conversion is done on the HbA1c value from the same draw, one tube of blood from a vein in your arm.

Repeating

After two to three months, not after days, because that is how long it takes for the red blood cells to be renewed. Repeating earlier mainly shows the measurement margin.

Which test

eAG (estimated average glucose) is in the comprehensive test (€229) and in core.

Where to draw

You can draw at 250+ locations near you, no referral needed. See the locations

Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.