Will I go blind? HbA1c can help measure the risk

THIS IS NOT TO SCALE! Illustrative chart to show how average blood sugar (HbA1c) is linked to the risk of developing complications.

THIS IS NOT TO SCALE! Illustrative chart to show how average blood sugar (HbA1c) is linked to the risk of developing complications.

Before I start, I’d like to remind you that I’m not a doctor and all my knowledge about diabetes comes from conversations with my doctor (which I may misremember) and Wikipedia. Oh, and personal experience!

When one is diagnosed with diabetes, it’s not long before the word “complications” is encountered. Diabetics are more likely to develop heart problems, eye problems (including blindness), kidney failure and ulcers in the feet. It is my understanding that consistently high blood sugar is a causal factor in all of these. So an important reason to measure blood sugar is that it allows a diabetic to assess how successful their blood sugar control is and whether they need to change anything.

An important test for this is the HbA1c test, first used in the Seventies. When the glucose content of blood is high (this can occur in a healthy person immediately after a glass of coke for example), glucose molecules attach to hemoglobin in the red blood cells. Red blood cells live for up to three months, so it is possible to find out how much glucose has stuck to the hemoglobin and therefore find a measure of average blood glucose levels over the past couple of months.

HbA1c can be expressed in different ways, but many people use a percentage. A healthy person will have an HbA1c of between 4% and 5.9%.

According to my doctor, the risks of developing complications rises exponentially as HbA1c rises. To understand what this means, just look at the graph on the top of this post. You can see that as HbA1c goes from 7 to 5.9, the risk of complications goes down by the amount in the lower shaded area on the left hand side. So the risk decreases but not by very much! If a diabetic has higher average blood sugar though, and their HbA1c goes from 11 to 10, then the risk of complications goes down by the higher shaded area on the left hand side of the graph.

What this means, is that if blood sugar is high, there are really big gains in terms of long-term health by controlling it better. If blood sugar is low (say HbA1c is 6.5%) then whilst risk does decrease by bringing blood sugar down, it doesn’t decrease by much. At these levels, other lifestyle factors such as smoking are much more important. (Another reason why diabetics have to eat a super healthy diet. Keeping cholesterol low, for example, is important in reducing the risk of heart disease.) So at low levels of HbA1c the costs of getting average blood sugar down further (increased risk of more hypos) probably outweigh the benefits. I will be advised by my medical team what balance to aim for, and other diabetics will be too – it depends on personal circumstances, sensitivity to hypos etc.

My doctor and I discussed all this in the context of heart problems, so I’m not 100% sure that the graph is the same for other complication such as eye problems.

I can’t remember what my HbA1c levels are. They are still too high. When I was diagnosed they were through the roof, and on my most recent visit last week they were much lower. (Dr Powrie was very complimentary saying how impressed he was with how much it had come down!) Anyway, I’m not going to worry about them yet. I’m sure (I hope) that a few months of high blood sugar around my diagnosis won’t make much difference to my risk of complications, and as I get things under control, my HbA1c should come down by itself.

Data What is type 1?