The Birmingham laboratory's Hb range is 130 to 171. Long before I was diagnosed with CML, I naturally sat at the bottom end.
Now, I range from 120 to 129, even with week-to-week variations.
On one occasion, my iron was low, and I had an infusion. More recently, my B12 was low, and I was directed to take a daily B12 tablet.
I was taking 2g of metformin a day for diabetes, and haematology requested my GP to reduce that to 1 gram.
Haematology, for me, does monitor all of the surrounding factors.
Whilst a GP considers low haemoglobin "abnormal" and a diabetes nurse considers low haemoglobin terrible, haematology is quite relaxed.
I am unsure whether diet makes much difference except that iron, B12 and folate may enter the equation.