The most common cause of low iron status in males, is poor acid content of the stomach. Chronic use of acid blocking drugs, or a tendency for achlorhydria (which runs in families) will lower absorption of iron because iron needs acid for absorption. I've seen some men in their 30's already showing up low in iron. This is becoming more common because of the overuse of Prilosec and Zantac type drugs.
After that is evaluated, then losing red cells thru the urine or GI tract comes next in frequency.
Then as Glenn pointed out, the more obscure things start lining up. One cause that is often overlooked is a parasitical disease that causes hemolytic anemias.
example:
http://en.wikipedia.org/wiki/Babesiosis
But usually there is fever associated with infections.
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Weezie looking at petunias 8.25.2017
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