Does hydration actually affect your TRT labs and muscle gains?

What did @_derek_fowler_ actually say?

Derek Fowler is telling TRT users who struggle with high hematocrit, what he calls "a hard time with your amount of equipment being high," to drink a half gallon to a full gallon of water before their blood draw. His argument is that doing so does not skew results. Instead, he says it "just proves that you're dehydrated." In other words, he is framing pre-draw hyperhydration not as a workaround but as a diagnostic correction.

That is a specific, testable claim. It implies that elevated hematocrit readings in TRT patients are primarily an artifact of dehydration rather than a genuine physiological effect of testosterone therapy. Let's unpack whether that holds up.

Does the science back this up?

Partially, but not cleanly. Dehydration does concentrate red blood cells, which can artificially inflate hematocrit values. That part is real. But the claim that high hematocrit on TRT is simply a hydration problem is not supported by the evidence.

Testosterone is well-documented to stimulate erythropoiesis, the actual production of more red blood cells, through erythropoietin signaling. This is a pharmacological effect, not a lab error. A 2014 study by Calof et al. in the Journal of Gerontology found dose-dependent increases in hematocrit in men receiving testosterone, independent of hydration status. Similarly, Bachman et al. (2010, Journal of Clinical Endocrinology and Metabolism) confirmed that testosterone-induced erythrocytosis is a direct biological response, not a measurement artifact. Drinking water before a blood draw may normalize hematocrit if the elevation was dehydration-driven, but it will not change your actual red blood cell mass if testosterone has genuinely raised it.

What did they get wrong (or right)?

Here is where it gets important to be precise, because Derek gets one thing right and one thing meaningfully wrong.

What he gets right: dehydration is genuinely underrecognized as a confounder in hematocrit readings. Many TRT patients train hard, sweat heavily, and show up to morning blood draws in a mildly dehydrated state. A 2020 review by Sanchis-Gomar et al. in the European Journal of Applied Physiology confirmed that even modest dehydration of 2 to 3 percent body water loss can elevate hematocrit by 3 to 5 percentage points. That is clinically meaningful.

What he gets wrong: his framing implies that a high hematocrit reading after drinking plenty of water is simply proof you were dehydrated before, and therefore the high reading was not real. That logic does not follow. If your hematocrit normalizes with hydration, yes, dehydration was a factor. But if it remains elevated after adequate hydration, that is a real finding that warrants clinical attention. Testosterone-induced erythrocytosis carries genuine thrombotic risk. Telling patients to hydrate and then dismiss high readings as a lab artifact is potentially dangerous guidance. It conflates two separate phenomena.

What should you actually know?

If you are on TRT and your hematocrit is running high, hydration matters as a baseline practice before any blood draw. Show up fasted but well-hydrated. That is just good lab hygiene and your clinician should be telling you this already.

But do not use hydration as a tool to game your labs. There is a meaningful difference between correcting a dehydration artifact and masking a real erythrocytosis. Hematocrit above 52 to 54 percent on TRT is a flag that warrants a real clinical conversation, not a hydration hack. Elevated hematocrit is one of the most common adverse effects of testosterone therapy and carries increased risk of blood clots, stroke, and cardiovascular events according to multiple FDA safety reviews and clinical guidelines from the Endocrine Society (Bhasin et al., 2018).

Your telehealth provider should be monitoring your complete blood count, not just total testosterone. If your numbers are consistently elevated even when properly hydrated, options like dose adjustment, frequency changes, or therapeutic phlebotomy exist and should be discussed with a licensed clinician.

• Hydrate consistently before blood draws as standard practice, not as a strategy to lower numbers.
• If hematocrit remains high after proper hydration, that finding is real and needs clinical evaluation.
• Do not delay reporting high hematocrit to your prescriber based on social media advice.