GP's are great aren't they! It is quite important to use units when writing to people on the forums.
Firstly, if you had a blood test which went off to a lab and 121mmol/mol is the result you got back. This will be what's called an hbA1c number and it's your average blood glucose level over the past couple of months. I will not lie to you, 121mmol/mol (millimol per mol) is quite bad.
If (on the other hand) you just had a finger prick test and the result is 121 mg/dl (milligrams per decilitre) then the result would be pre-diabetic for a fasting level which is not serious. It would be difficult to infer anything else without knowing what you'd eaten and when.
Hi @Tim0001 , in addition to the info that @urbanracer has asked, can you also let us know if your GP mentioned which type of diabetes you have and any medications he has prescribed? This will help us to help you.