Glycated Hemoglobin-HbA1c

Glycated Hemoglobin - HbA1c




HbA1c test is also named hemoglobin A1c test, glycated hemoglobin test, or glycohemoglobin.  It is an important blood test indicating diabetes condition.  Hemoglobin A1c shows an average of blood sugar control over the past 2 to 3 months.  It is used along with home blood sugar monitoring to make adjustments in diabetes medicines.

Hemoglobin in red blood cells carrying oxygen circulating in human body.  When diabetes is not under control, i.e. blood sugar being too high, sugar builds up in bloodstream and combines with hemoglobin, becoming “glycated 糖化.”   The average amount of sugar blood can be discovered by measuring hemoglobin A1c level.  If glucose levels have been high over recent weeks, the hemoglobin A1c test will be higher.


HbA1c refers to glycated haemoglobin.  It develops when haemoglobin, a protein within red blood cells that carries oxygen throughout human body, joins with glucose in the blood, becoming ‘glycated’.

By measuring glycated haemoglobin (HbA1c), clinicians are able to get an overall picture of the average blood sugar levels over a period of weeks/months.

This is important to diabetics as the higher the HbA1c, the greater the risk of developing diabetes-related complications.

HbA1c is also referred to as haemoglobin A1c or simply A1c.

HbA1c – Measurement of Average Blood Glucose
When human body processes sugar, glucose in the bloodstream naturally attaches to haemoglobin.  The amount of glucose that combines with this protein is directly proportional to the total amount of sugar that is in the system of human body at that time.

It is because red blood cells in the human body survive for 8-12 weeks before renewal, measuring glycated haemoglobin (or HbA1c) can be used to reflect average blood glucose levels over that duration, providing a useful longer-term gauge of blood glucose control.

If blood sugar levels have been high in recent weeks, HbA1c will also be greater.

HbA1c Targets


20-41 mmol/mol (4-5.9%) – without diabetes
48 mmol/mol (6.5%) – with diabetes but under good control
59 mmol/mol (7.5%) – at greater risk of hypoglycemia


Benefits of lowering HbA1c
Two large-scale studies – the UK Prospective Diabetes Study (UKPDS) and the Diabetes Control and Complications Trial (DCCT) – demonstrated that improving HbA1c by 1% (or 11 mmol/mol) for patients with type 1 diabetes or type 2 diabetes cuts the risk of microvascular complications by 25%.

Improving HbA1c by 1% (or 11 mmol/mol) for patients with
type 1 diabetes
type 2 diabetes

reduces the risk of microvascular complications by 25%.
Microvascular complications include:
Diabetic nephropathy (kidney disease)

For patients suffering type 2 diabetes to reduce HbA1c level by 1% are:
19% less likely to suffer cataracts
16% less likely to suffer heart failure
43% less likely to suffer amputation or death due to peripheral vascular disease


Difference between HbA1c and Blood Glucose Level
1) HbA1c
an average, provides a longer-term trend of blood sugar levels over a period.  Its reading can be taken on blood sample from finger or from arm.

2) Blood glucose level
the concentration of glucose in blood at a single point in time, i.e. the very moment of the test.  This is measured using a fasting plasma glucose test, which can be carried out using blood taken from a finger or can be taken on a blood sample from the arm.

However, fasting glucose tests indicate current glucose levels only, whereas HbA1c test serves as an overall marker of average levels over a period of 2-3 months.  HbA1c can be expressed as a percentage (DCCT unit) or as a value in mmol/mol (IFCC unit).

Compariosn – DCCT-HbA1c and IFCC-HbA1c


HbA1c value, measured in mmol/mol, should not be confused with a blood glucose level, measured in mmol/l.

HbA1c Converter      clickhere_orange


Comparison HbA1c and Blood Glucose Levels


Since blood glucose levels fluctuate constantly on a minute by minute basis, regular blood glucose testing is required to understand how the levels changing through the day in order to learn how different meals affecting glucose levels.


Video     clickhere_blue



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