High hematocrit on TRT: what actually works and what doesn't

What did @kmartfit actually say?

The claim is straightforward: if you're on TRT and getting high hematocrit readings, you might just be showing up to the lab dehydrated. @kmartfit says "you gotta be drinking 64 ounces of water before you get a blood test done" to get accurate red blood cell, hematocrit, and hemoglobin numbers. He frames this as a fix, or at least a diagnostic step, before assuming your TRT is actually causing the elevation.

To be fair, he's not saying hydration cures polycythemia. He's saying dehydration can produce a false positive, and that you should rule it out first. That's a narrower, more defensible claim. But the way it's packaged, as a solution to high hematocrit rather than a troubleshooting step, matters a lot when 72,000 people are watching.

Does the science back this up?

Partially, yes. Dehydration genuinely can concentrate blood and produce falsely elevated hematocrit readings. This is not controversial. The problem is that the 64-ounce number is pulled from thin air, and the framing buries a more serious issue.

Hematocrit is a percentage measurement of red blood cells relative to total blood volume. When you're dehydrated, plasma volume drops, so the ratio shifts upward even if your actual red blood cell count hasn't changed. This is called relative erythrocytosis, and it's real. A 2019 review by Caglar et al. in the International Journal of Laboratory Hematology confirmed that pre-analytical variables including hydration status meaningfully affect hematocrit results. Labs generally recommend adequate hydration before blood draws for this reason.

However, testosterone therapy also causes true, absolute erythrocytosis by stimulating erythropoietin production and suppressing hepcidin, which increases iron availability for red blood cell synthesis. This is well-documented. Bachman et al. (2014, Journal of Clinical Endocrinology and Metabolism) found testosterone dose-dependently increased hematocrit in healthy men. Drinking water will not fix that.

What did they get wrong (or right)?

He got the mechanism right but the framing wrong, and that gap is clinically meaningful.

Credit where it's due: dehydration as a confounding variable in hematocrit readings is legitimate and underappreciated. Many men do show up to fasted morning labs without adequate hydration, which can inflate numbers. Checking hydration status before assuming TRT is the culprit is reasonable advice.

But calling this a way to "fix" high hematocrit is misleading. If your hematocrit is running 52-54 percent on TRT, you are not dehydrated. You have testosterone-induced erythrocytosis, and no amount of water addresses that. The actual clinical management of persistent high hematocrit on TRT includes dose reduction, changing injection frequency, switching delivery method, or therapeutic phlebotomy. None of that was mentioned.

There's also no clinical basis for the specific 64-ounce figure. Standard pre-draw hydration recommendations vary by lab and context. Presenting a specific number as fact without a source is the kind of thing that sounds authoritative and isn't.

What should you actually know?

High hematocrit on TRT is one of the more clinically significant side effects of testosterone therapy, and it deserves more than a hydration hack.

Testosterone increases red blood cell production through multiple pathways. Hematocrit above 54 percent is generally considered a threshold for clinical concern because of increased blood viscosity and associated cardiovascular risk, including stroke and thromboembolism. A 2023 analysis by Guo et al. in the Journal of the American Heart Association found elevated hematocrit was associated with increased adverse cardiovascular events in men on testosterone therapy.

If your hematocrit is borderline and you're unsure about your hydration status at the time of the draw, yes, repeat the test well-hydrated. That's sensible. But if you're getting consistently elevated readings across multiple draws, that is a conversation for your prescribing clinician, not a TikTok fix. Dose adjustments, injection frequency changes, and in some cases phlebotomy are the actual tools here. Hydration is a pre-analytical control, not a treatment.