Why Donating Blood on TRT Makes High Hematocrit Worse

Why Donating Blood on TRT Might Not Fix Your High Hematocrit

If you're on TRT and your hematocrit is high, don't give blood. At least not as a reflex, and not before you understand what the donation is actually doing inside you.

The standard advice is simple and it comes from a reasonable place. Your hematocrit climbs, the number on the panel looks alarming, so you remove some blood and the number comes down. It works on paper because you have physically taken red cells out of circulation, and the next lab draw reflects that.

And there's actually a 2024 review that directly challenges that. I cannot point you to the full text here, so treat this as the way I read the argument rather than settled literature, but the reasoning it lays out matches what I see in practice.

Here is the chain, start to finish, before we zoom in on any one link.

Testosterone raises red blood cell production. Red blood cells are built out of iron. You donate blood, you lose iron with it. Low iron changes how much oxygen your tissues are getting. And low tissue oxygen is the exact signal your kidneys use to decide it is time to make more red blood cells.

So basically what you're doing is you're treating a symptom that reinforces the cause.

And so what that study found is that when you give blood, what it does is it depletes your iron stores. This is not a subtle effect either, because a single whole blood donation takes roughly 200 to 250 milligrams of iron with it, and your entire storage pool might only be a few hundred milligrams to begin with. In women of reproductive age, repeated losses of that size are the main driver of iron deficiency worldwide, and the storage pool empties long before hemoglobin drops enough to flag on a standard panel. (Coad and Pedley, 2014)

Low iron lowers tissue oxygen partial pressure.

That last part is the piece most people miss, because they think of iron as something that only matters if you are anemic. Iron is not just cargo space for oxygen. It sits inside the enzymes your cells use to sense how much oxygen is actually present, and when iron drops, those sensors start reporting a low-oxygen environment whether or not you are truly hypoxic.

Your body reads low tissue oxygen as a signal to produce more red blood cells.

The kidneys respond to that reading by ramping up production of a hormone that tells your bone marrow to build more red cells. So the donation lowers your hematocrit on Tuesday and turns up the production signal for the weeks that follow.

Every time you give blood, your body responds by creating more red blood cells. You're creating more of the problem by giving blood.

You pair that on top of the increase in EPO signal from the kidneys, from the testosterone injections. And now you're basically doubling down on the problem that you created with causing the high hematocrit. I want to be careful here, because no study has shown that combination effect measured directly in TRT patients, so this is mechanism plus what I see with clients, not a controlled trial. And the more blood you give, the bigger the problem you create.

What to do instead starts with checking the actual driver rather than the number. Pull ferritin and iron saturation alongside your hematocrit, because if ferritin is already low and hematocrit is high, you are looking at someone whose body is being told to build red cells it does not have the material for, and taking more blood makes that instruction louder.

Then look at your dose and your injection frequency, since the erythropoietic response tracks with the peaks, and smaller more frequent doses produce a flatter curve.

Then look at sleep apnea, because untreated apnea drops oxygen saturation for hours every night and that is a real hypoxic signal, not a false one.

Research: Coad J, Pedley K. Iron deficiency and iron deficiency anemia in women. Scand J Clin Lab Invest Suppl. 2014.

References:

Coad J, Pedley K. Iron deficiency and iron deficiency anemia in women. Scand J Clin Lab Invest Suppl. 2014. https://pubmed.ncbi.nlm.nih.gov/25083899/