How

[pravin555]

how glycosylated haemoglobin (Hb A 1c) blood test calculates 3 months average said glucose and estimated average glucose ? is it random glucose ?

[barry1010]

I don't know but Google says:

"The sugar in your blood is called glucose. When glucose builds up in your blood, it binds to the haemoglobin in your red blood cells. The A1c test measures how much glucose is bound.

Red blood cells live for about 3 months, so the test shows the average level of glucose in your blood for the past 3 months.

If your glucose levels have been high over recent weeks, your haemoglobin A1c test will be higher."

https://www.webmd.com/diabetes/guide/glycated-hemoglobin-test-hba1c