Short answer: Often yes, in the US. The American Red Cross eligibility list does not name testosterone, and it says that in almost all cases medications do not disqualify a donor; eligibility depends on why the medicine was prescribed. Its HIV-risk rules ask people who injected steroids or anything not prescribed by their doctor in the past 3 months not to give blood. Every donor must also pass a hemoglobin check, which is capped at 20 g/dL.
The Red Cross publishes an A to Z list of eligibility rules. Testosterone does not appear on it. Its general rule on medicines reads: "In almost all cases, medications will not disqualify you as a blood donor." It goes on to say that eligibility is based on the reason the medicine was prescribed, and that donation is usually permitted as long as the condition is under control and you are healthy.
The list then names a short set of drugs that need a waiting period after the last dose. Testosterone is not one of them. Blood centers other than the Red Cross, and blood services in other countries, set their own rules within national law, so the center you visit has the final say.
The prescription matters. Under its HIV section, the Red Cross says you are at risk, and should not give blood, if in the past 3 months you "have used needles to inject drugs, steroids, or anything not prescribed by your doctor". The same applies to sexual contact with someone who has done so.
So testosterone injected under a prescription falls under the general medication rule, while injecting steroids without a prescription means waiting 3 months from the last injection. The rule is about infection risk from needles, not about testosterone itself. Expect the screener to ask about medicines and injections at the visit.
Every donor has hemoglobin (or hematocrit) checked before giving blood. FDA rules (21 CFR 630.10) set the minimums: for men, hemoglobin of at least 13.0 g/dL or hematocrit of at least 39%; for women, at least 12.5 g/dL or 38%.
The Red Cross uses the same minimums and adds a ceiling: hemoglobin can be no higher than 20 g/dL for any donor. A Power Red donation needs at least 13.3 g/dL.
This is where testosterone comes in. Testosterone raises red blood cell production. The Xyosted label says to check hematocrit before starting, about every 3 months during treatment, and to stop the drug if hematocrit becomes elevated until it comes back down. The Depo-Testosterone label says hemoglobin and hematocrit should be checked periodically in long-term use. A 2011 review found the effect on red cell production shows by about 3 months and peaks at 9 to 12 months.
Giving blood removes red cells, so men on TRT often ask whether regular donation can keep hematocrit down. The labels do not list blood donation as a step. Their step for a high hematocrit is to pause or stop the testosterone product, and the Endocrine Society guideline names an elevated hematocrit as a reason not to start testosterone therapy.
A blood donation is a gift to the blood supply, run under donor rules, not a medical treatment planned around your levels. If your hematocrit is high, that is a conversation for your prescriber, who can weigh the options. If you do donate, write the date down next to your lab results, since a recent donation can change the next reading.
Read more on Dose Track: Hematocrit on TRT: when to test · Hematocrit (glossary) · Xyosted side effects · Depo-Testosterone side effects · Testosterone cypionate guide · Low testosterone