It is per mol of total Hb.

Thank you very much, Dr. James Leigh 

For conversion by  IFCC percentage  and NGSP  mmol/mol units

http://www.ngsp.org/convert1.asp

Dear doctors, I really need help, how can I convert between HbA1C  from nmol/ L plasma ( which I already have my results in)  

to

mmol/mole hemoglobin? 

You also will need the plasma total Hb in nmol/L. (1g/dL Hb = approx 0.6206 mmol/ L= 620.6 nmol/L.)

then HbA1C (%) = HbA1C (nmol/L)/ Hb (nmol/L)

Thank you, Dr. Leigh, for your fast response.

Would you please recommend an accurate, simple and cheap chemicals method for determination of plasma Hb?

See attached. Note correction to previous answer also HbA1C (%) = HbA1C (nmol/L)/ Hb (nmol/L) x 100