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HbA1c Explained: What Your Blood Sugar Test Really Means

HbA1c Explained: What Your Blood Sugar Test Really Means
How is HbA1c calculated? Expert explains what your blood sugar test really means · indianexpress.com

HbA1c is a blood test that shows how much sugar has stuck to your red blood cells.

Red blood cells usually live for about three months.

That is why the test gives a longer-term picture of blood sugar.

It is not calculated by simply averaging fasting and after-meal readings.

Newer blood sugar levels affect the result more than older levels.

An HbA1c of 7 percent means about 7 percent of the measured haemoglobin is glycated.

It does not mean that blood sugar stayed at 7 percent all day.

A formula can estimate the average glucose level from the HbA1c result.

Some health conditions and blood-related changes can make the result less reliable, so doctors may compare it with other tests.

Key facts

What HbA1c measures
The percentage of measured haemoglobin that is glycated, or attached to glucose.
Typical time period
The preceding two to three months.
Reporting format
Usually reported as a percentage.
HbA1c example
An HbA1c of 7 percent means approximately 7 percent of measured haemoglobin is glycated.
Estimated average glucose formula
eAG (mg/dL) = 28.7 × HbA1c − 46.7.
Estimated glucose examples
HbA1c of 6 percent corresponds to about 126 mg/dL; 7 percent corresponds to about 154 mg/dL.
Possible limitations
Red-cell lifespan changes, haemoglobin variants, recent blood loss or transfusion, and some medical conditions may affect the result.

Quotes

Dr Pranav Ghody

Consultant endocrinologist and diabetologist at Wockhardt Hospitals, Mumbai Central

“It is a laboratory measurement of how much glucose has attached to haemoglobin in your red blood cells. Since red blood cells circulate for roughly three months, the HbA1c value gives us an idea of a person’s average blood glucose over the preceding two to three months,”
indianexpress.com
“HbA1c is extremely useful, but it should not always be interpreted in isolation. Conditions that alter the lifespan or turnover of red blood cells, certain haemoglobin variants, recent blood loss or transfusion, and some other medical conditions can affect the result.”
indianexpress.com

Sources

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