This is the problem with health forums, one starts off with assumptions that are inaccurate and statements are made which accentuate the misconceptions.
First of all, those results are NOT for iron levels but represent Haemoglobin levels......different things. Hb 6 is very low and needed investigation and transfusion. What type of anaemia and if iron deficiency, then why?
No amount of tablets will rectify that level of Hb.
\\\\.I know when it's really low as my tongue starts to 'hurt'...is it normal that low iron affects the tongue?\\
Are you saying that your Hb fluctuates?
In answer to your question....it MIGHT be that the low HB causes a sore tongue, but that is a minor detail compared to the reason for the low HB.
I don't know anything about your past history e.g if you have heavy periods, but ask the GP what type of anaemia it is and what is causing it.