Ferritin is the best way to measure the body's iron store. In iron deficiecy anemia and the prelude to it (where you likely are), the ferritin falls first as a result of iron deficicency. For anemia, a fall in hemoglobin below 12 is the marker, along with an MCV below 80 (microcytic). If it is caused by iron deficiceny, then it is "iron deficiency anemia" IDA.
Concerning what level defines iron deficiency or iron depletion without anemia, I had bookmarked some articles on the subject for myself. Some of the articles are very technical and narrowly focused, but contain gems of info on the standard being used to define
iron deficiecy/ depletion within that article/study.
I did check with the rules of posting and it says posting books and authors is fine, so I presume the same is true about journal articles and titles. Most of the articles I mention are available in full text on the web.
American Journal of Clinical Nutrition, Vol 77 441-448 February 2003, Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women
, states iron depletion is at <20 ug/ serum ferritin
Journal of the American College of Nutrition, Vol 21 545-552 2002, Non-Anemic Iron Depletion, Oral Iron Supplementation and Indices of Copper Status in College-Aged Females
, states <20 ug/ serum ferritin
Same journal Vol 20,477-484 2001 Can Dietary Treatment of Non-Anemic Iron Deficiency Improve Iron Status?
states that mild iron deficiiency is serum ferritin <20 µg/L and hemoglobin >=120 g/L
If you dr need more heavy hitters outside the nutriition world, then how about Blood? the premier journal of that big association of hematologists?
Blood, February 15 2006, Vol107, 1673-1679, Variable hematologic presentation of autoimmune gastritis: age-related progression from iron deficiency to cobalamin depletion
states deficiency is serum ferritin level less than 15 µg/L.
Same journal February 15 2002 Vol 99, pp1489-1491, Clinical utility of the reticulocyte hemoglobin content in the diagnosis of iron deficiency
stated that serum ferritin of 12 µg/L
or less is the most specific indicator of iron deficiency.
For a really good general read
that your dr would most likely see, check out American Family Physician Vol. 62 No. 7 October 1, 2000, Anemia in the Elderly
say iron def is at serum ferritin is less than 15 ng per mL
(15 µg per L)
Another good read : same journal Vol. 75 No. 5 March 1, 2007, Iron Deficiency Anemia
Lastly, if your dr says "so, you are iron deficiient, but you don't have anemia", let him know there are tons of articles out there on decreased work ability and increased fatigue in iron deficiiency without anemia. See: BMJ 2003;326:1124, 24 May, Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial
shows that there was a benefit from supplementation in people with less than 50 ferritin
Ok. hope this is helpful. It took me a while to gather all this info, and I figured I would share it and put it to good use.