While a complete blood count (CBC) is considered part of routine bloodwork, testing for Ferritin (a protein that stores iron) is usually reserved only when the CBC shows low hemoglobin.
Unfortunately, this approach can miss what has been termed a "hidden disorder" known as Hypoferritinemia without anemia, or in other words, iron deficiency with normal hemoglobin. A condition that exhibits many of the same symptoms as iron deficiency anemia, including fatigue, fast heart rate and palpitations.
How rare it is I don't know, but not rare enough for me to have recently been diagnosed with it!
Long story very short, no bleeding source was found via colonoscopy endoscopy (I was due anyway) and within a month or so my Ferritin returned to normal. The working hypothesis -- and it's only that because of the timing -- is that I had a GI bleed while on AC's (anti-coagulants) and the Ferritin returned to normal when I went off the AC's. The colonoscopy and endoscopy were performed when I was off AC's for over a month so showed no bleeding.
My very non-professional opinion on all this is that anyone on AC's should probably periodically not only have a CBC but also an iron stores panel as well that includes testing for Ferritin. And especially if you have symptoms of iron deficiency anemia. I know I will.
Someone is probably going to ask why I'm not on AC's now, but that's not what this post is all about. It's about people on AC's being aware that bleeding is a possible side effect of AC's and that periodic testing for that possibility makes a certain sense. At least it does now for me.
Jim