Should I be worried about my fasting test?

Apologies if this is the wrong place to ask etc, but I have been booked in for a fasting blood glucose test on tuesday morning, and my GP has asked for HbA1C to be tested too (I am not a diabetic yet, but my mother is a T1 for 32 and a half years and my grandmother , my mums mum, is a T2 for 20 years almost), due to me seeing blood glucose results of at the highest, 10.9mmol after a relatively healthy Salad roll (Relatively healthy being a cracked wheat roll, lettuce, tomato, cucumber, a slice of ham and some margarine).

The lowest my sugars have been lately, is 4.8.

My question is, what exactly will the HbA1c show? My gp has also asked for a fasting glucose test (not the glucose tolerance, just a bog standard water from midnight test), but from checking myself, my fasting sugars havent peaked much past 6.2mmol.

I am extremely worried about this, because if it does indeed show that I am diabetic, I dont know how this will react with my Pernicious Anaemia (accompanied with extremely low folates) or the nerve damage that has resulted from this already.

Hmm to google it is then.

I'd originally made the first appt with my GP on advice of the Practice Nurse, who I'd mentioned that I kept getting burning sensations in my hands and feet (my feet and lower legs are already affected by Pernicious Anaemia related Neuropathy) and she insisted that I make an appt to get that checked out, which is when my GP ran the initial blood test primarily to check B12 levels, but she also checked stuff like Folates (which were 1.3 and according to GP Very low), liver function, blood glucose etc, which is when she discovered the borderline diabetes as the sugar came back as 6.2mmol.

After getting the blood results, I started randomly testing my sugar each day, sometimes 2 hours after a meal, and quite often before I'd eat, to see if there was some pattern of them going high.

The 10.9mmol result came roughly 2 hours after a meal, I checked the sugar level then because I'd started feeling unwell, and it was accompanied by the most god awful headache too.

When I saw my GP on the 13th of this month, I mentioned that 10.9mmol result to her, and she said that eating a salad roll really shouldnt have impacted my sugars to be that high as most normal people can cope with that, which is why she ordered a fasting test and an HbA1c test.

She now also thinks that a lot of the symptoms Ive had from the PA (the nerve issues, tiredness, headaches, urinary problems etc) could be related to the blood sugars, even though I was experiencing those 2 years ago when the blood sugars were coming back normal on labwork.