Hi Khanh Nam,
It looks like you are referring to blood glucose levels which can be quoted in either mg/dl or mmol/l and measured typically by using a blood glucose monitor - it gives a point in time measure so is useful to track fluctuations in BG levels, response to eating foods, especially carbohydrates, exercise, etc. Many diabetics self monitor with their own meters.
However this thread is referring to the HbAc1 test, which is an indirect test based on the accumulation of sugars on red blood cells and gives an indication of the average BG levels over the past 2-3 months. It cannot provide any information on how widely the BG fluctuates during this period.
It is reported as either mmol/mol or as a %.
From Diabetes.co.uk site :
http://www.diabetes.co.uk/what-is-hba1c.html -->
"How does HbA1c differ from a blood glucose level?
HbA1c provides a longer-term trend, similar to an average, of how high your blood sugar levels have been over a period of time.
An HbA1c reading can be taken from blood from a finger but is often taken from a blood sample that is taken from your arm.
Blood glucose level is the concentration of glucose in your 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 from a blood sample from the arm.
However, fasting glucose tests provide an indication of your current glucose levels only, whereas the HbA1c test serves as an overall marker of what your average levels are 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). Since 2009, mmol/mol has been the default unit to use in the UK.
Note that the HbA1c value, which is measured in mmol/mol, should not be confused with a blood glucose level which is measured in mmol/l. Use our HbA1c conversion tool to help with switching between the two measurement units. "
Hope this helps!