HbA1c is a term often used in relation to diabetes and this guide explains what HbA1c is, how it's used for diabetes diagnosis and how it differs from blood glucose levels.

What is HbA1c?

HbA1c occurs when haemoglobin joins with glucose in the blood. Haemoglobin molecules make up the red blood cells in the blood stream.

When glucose sticks to these molecules it forms a glycoslated haemoglobin molecule, also known as A1c and HbA1c.

The more glucose found in the blood the more glycated haemoglobin (HbA1c) will be present.

How does HBA1c return an accurate average measurement?

Due to the fact that red blood cells survive for 8-12 weeks before renewal, by measuring HbA1c, an average blood glucose reading can be returned.

  • For non-diabetics, the usual reading is 4-5.9%.
  • For people with diabetes, an HbA1c level of 6.5% is considered good control, although some people may prefer their numbers to be closer to that of non-diabetics.
  • People at greater risk of hypoglycemia may be given a target HbA1c of 7.5%

This prevents too many low blood sugars from occurring.

When should HbA1c level be tested?

How often HbA1c levels should be taken depends on the person with diabetes and their history of control and treatment objections.

Generally, the following are considered best practice in HbA1c regularity.

  • Once per 3 months if trying to get better control.
  • Once per 6 months if good control achieved and maintained.

There is little point in having HbA1c checked regularly if you are not making efforts to control your diabetes.

Although HbA1c level alone does not predict diabetes complications, good control is known to lower the risk of complications.

How does an HbA1c show poorly controlled diabetes?

In well-controlled diabetes without a high level of glucose in the blood, a lower level of glycosylated haemoglobin will be returned.

hba1c album
Fig 1: HbA1c & Glucose Blood Levels

Ave. Blood Glucose
13 119 18 mmol/L
12 108 17 mmol/L
11 97 15 mmol/L
10 86 13 mmol/L
9 75 12 mmol/L
8 64 10 mmol/L
7 53 8 mmol/L
6 42 7 mmol/L
5 31 5 mmol/L

If people with type 2 diabetes reduce their HbA1c level by 1%, there is a [1]:

  • 19% reduction is cataract extractions
  • 16% decrease in heart failure
  • 43% reduction in amputation or death due to peripheral vascular disease

In the case of poor control, with more glucose, a higher level of glycosylated haemoglobin will be returned.

But glucose level change all the time, don’t they?

Blood glucose levels fluctuate constantly, literally on a minute by minute basis.

Therefore, for micro adjustments and regular checking, blood glucose testing is advised.

The HbA1c level changes very slowly over a 10 week period.

How do blood glucose levels compare with HbA1c?

The table on the right (figure 1) shows how average blood sugar levels in mmol/L would be translated into HbA1c readings, and vice versa.

Reference: www.diabetes.co.uk