I must be missing something basic here.
Tired All The Time or TATT is an acronym often seen and often associated with an anaemia, the most common type of which is Iron Deficiency Anaemia.But- for anaemia to be profound enough to induce such listlesness, you would certainly expect to see an abnormal blood test.
You go on to say that your are taking tabs ( by which I assume you mean iron tablets) as your Dr. said you were low on iron.
Here is where I get a bit confused though - you say that "nothing showed up on tests at the Dr." - but if you have an iron deficiency anaemia diagnosed by your Dr, then I would have expected an abnormal Full Blood Count with a low Haemoglobin. Unless you have a low Haemoglobin, I really do not understand why you would be prescribed iron tablets.
In further posts, I get more confused :) I think I understood you to say you had started taking iron tablets of your own accord, before you went to see the Dr. So does the Dr know you are taking iron tablets? Did they prescribe them?
Otherwise, I would agree with Sqad, especially wrt B12 anaemia - very characteristic blood film and markers from the Full Blood Count, such as Mean Cell Volume ( MCV) for instance...
So the questions I would have are;
1. Has the Dr. diagnosed you as suffering from anaemia?
2. Has the Dr. presribed a course of supplementary iron therapy?
3. Was the blood test for anaemia abnormal?
If you do have iron deficiency, and have been presribed iron supplements, then any improvement will take some time - typically several days if not weeks. And I would certainly expect the Dr. to investigate the cause of your anaemia- is it due to bleeding, or impairment of the iron transport/absorbtion system, or simply an insufficiency of iron in the diet?
@Solvitquick - You said something in your post which i do not understand - you said that "like vitamin B12 status which is needed for dietary iron absorption" - Can you explain how B12 is involved in dietary iron absorption? First I have heard of it :)