Just in case it hasn't been posted before:
It is well documented that iron anaemia can mask B12/folate deficiency including being mentioned by NICE but not so much the other way around. Being convinced that my Mum must be iron deficient and pondering whether her folate and possible B12 deficiency might be masking it, I found this published in 2015 and thought it was interesting and useful to those in this situation who have ongoing problems and have not had their ferritin levels retested etc as assumed normal.
Basically, out of a group of 75 people with B12 deficiency, only 9.3% showed indications of iron deficiency in their blood tests including ferritin, blood counts and iron panels before treatment for the B12 deficiency. After treatment for the B12 deficiency, the amount of people indicating iron anaemia in their blood tests rose to 49.3%.
For example, in regards to the 37 people who tested positive for iron deficient anaemia after B12 treatment, their mean ferritin result was 124.3 before B12 treatment and only 25.6 after B12 correction. The same marked differences showed in other tests such as the serum iron.
However, they could not determine a significantly reliable way of testing for this before B12 treatment although possibly because of the limitations of their research so concluded that iron anaemia can be masked and only emerges after B12 treatment and therefore iron deficiency anaemia should be retested for after the B12 deficiency is corrected. They indicated that it took 1-3 months for the iron deficiency to reveal itself but bear in mind that this was treatment by injection with a loading dose and continued maintenance doses so might not apply to other forms of possibly less effective supplementation maybe?
Anyway, apologies if already posted