Does hematocrit actually tell you when to donate blood on TRT?

What did @cbronsonmd actually say?

The claim is straightforward: scheduled blood donation on TRT is wrong, and you should only donate based on your hematocrit reading. Specifically, he sets 55% hematocrit as the trigger threshold, pairs it with a ferritin check above 30-40, and recommends retesting every three months. He calls clinics that schedule routine donations every 8-12 weeks "morons" who "don't know what they're doing."

The core argument is that indiscriminate phlebotomy, particularly on a fixed calendar schedule, ignores actual lab values and can create problems of its own, especially iron depletion. That is not a fringe position. It is, in fact, closer to the emerging clinical consensus than the rotate-and-donate approach many TRT clinics still use.

Does the science back this up?

Mostly, yes, with some important nuance. The hematocrit-first approach has real support, and the concern about over-donation causing iron deficiency is documented in the literature.

A 2014 paper by Bachman et al. in the Journal of Clinical Endocrinology and Metabolism examined cardiovascular risk thresholds in testosterone-treated men and noted hematocrit above 54-55% as the point where polycythemia risk becomes clinically relevant. The Endocrine Society's clinical practice guidelines (Bhasin et al., 2018, JCEM) recommend checking hematocrit at 3-6 months after initiation and then annually, and suggest therapeutic phlebotomy or dose reduction if hematocrit exceeds 54%. The 55% threshold he uses is slightly above the Endocrine Society's 54% cutoff, which is worth flagging.

On the ferritin side, Coates et al. (2017, Transfusion) demonstrated that frequent whole-blood donation reliably depletes iron stores, sometimes to levels that cause fatigue and cognitive symptoms even before anemia appears. That is the real harm of reflexive scheduling, and he is right to call it out.

What did they get wrong (or right)?

He got the core principle right. Scheduled phlebotomy without lab guidance is not evidence-based practice, and the ferritin pairing is legitimately good clinical thinking. Give him credit for that.

However, the 55% threshold deserves scrutiny. The Endocrine Society and most published guidelines use 54% as the intervention point, not 55%. That one percent difference may sound trivial, but at a population level it means some patients are being told to wait slightly longer than guidelines recommend. It is not a dangerous error, but it is an imprecision.

The ferritin cutoff of "30 to 40" is also on the loose side. Many labs flag ferritin below 30 ng/mL as low-normal, and some guidelines use 50 ng/mL as a floor for iron sufficiency in active individuals. Donating when ferritin is sitting at 31 could push someone into symptomatic iron deficiency faster than he implies.

His tone toward other clinics is blunt, but the underlying critique is fair. Reflexive 8-week donation schedules have no strong guideline backing and do carry real iron-depletion risk.

What should you actually know?

If you are on TRT, hematocrit and ferritin should both be on your lab panel, not just testosterone and PSA. Testing every three months during dose adjustments is reasonable; annually may be sufficient once stable, per Endocrine Society guidance.

The actionable thresholds from published guidelines: consider therapeutic phlebotomy or a dose conversation with your prescriber if hematocrit exceeds 54% (Bhasin et al., 2018). Do not donate blood if your ferritin is already low, because you will accelerate iron deficiency without meaningfully reducing cardiovascular risk.

Phlebotomy is not the only tool. Dose reduction, switching delivery method, or splitting doses can also bring hematocrit down. A clinician who reaches for the Red Cross appointment before discussing dose adjustment is skipping a step.

• Hematocrit above 54% is the published guideline threshold, not 55%.
• Ferritin below 30 ng/mL is a reason to hold off on donation, not a green light.
• Scheduled phlebotomy without lab testing has no strong evidence base.
• Iron deficiency from over-donation is a real documented risk, not a hypothetical.