04/05/2026
Tired? Cold? Feel like your thyroid is low but it isn't? It might be iron deficiency. Iron is a critical element used in virtually every part of the body. 25 years ago, it was thought that iron primarily mattered for red blood cells, thus if you weren't anemic, you were "fine." Now we know better.
Around 2001, research demonstrated that iron is incorporated directly into the developing brain of children, especially under age 2 years, making this a critical time for optimal iron status.
Since then, the role of iron has been demonstrated in multiple other tissues, including your immune system, brain, hormones (including thyroid), and basically everything else.
Laboratories continue to report the storage transporter for iron, "ferritin," as being normal if it's above 12 or 15. However the medical literature has long disputed this. Kids who are otherwise healthy should have a ferritin above 30. Kids with neurologic, psychiatric, developmental, or connective tissue disorders should target a ferritin above 50. Kids with a history of significant or refractory iron deficiency will likely also benefit from a higher ferritin, above 50. Last year, the American Gastroenterological Association recommended that the lower limit of ferritin be set at 45 for adults. In our practice, we generally set the upper limit around 100, although some people consider 150 to be acceptable.
Note that ferritin is an inflammatory marker, so it can be spuriously elevated even in situations like having a minor viral illness. In fact, it's a pretty labile molecule that acts kind of like a prima donna. This can make it hard to pin down, and you might have levels that seem pretty good but which are actually reflecting inflammation rather than excellent iron status. One clue is to look at your iron saturation. If it's low, but your ferritin is normal or high, then this might be a sign of inflammation.
