How this instrument works
Blood donation eligibility in the United States runs through a general regulatory framework — FDA rule 21 CFR 630.10 requires donors to be in good health and free from transfusion-transmitted infection risk — layered under blood-bank-specific criteria. The American Red Cross publishes a widely used set of basic numeric thresholds covering age, weight, and hemoglobin that function as an early check before the full donor health history screening.
This calculator applies three of those thresholds: a minimum age of 17, a minimum weight of 110 lb (about 50 kg), and a hemoglobin minimum of 12.5 g/dL for women or 13.0 g/dL for men — reflecting the normally lower hemoglobin range in women and keeping the amount of hemoglobin removed during a standard whole-blood donation within a safe margin for each group.
Two things this calculator does not model are worth stating plainly. First, the age check is a flat 17-or-older cutoff — several U.S. states allow 16-year-olds to donate with signed parental or guardian consent, and that state-by-state exception isn't implemented here. Second, these three numbers are only a starting screen: real donor eligibility also depends on recent travel history, current medications, certain health conditions, recent tattoos or piercings, recent vaccinations, pregnancy status, time since a prior donation, and other factors covered by the confidential health history questionnaire and brief physical check at the actual donation site. Treat a passing result here as necessary, not sufficient — check with your local blood bank or the Red Cross directly for a full eligibility assessment.
- Enter the donor's age, in years.
- Enter weight in pounds.
- Select whether the donor's sex is female — this determines which hemoglobin threshold applies.
- Enter the most recent hemoglobin reading, in g/dL.
- Read whether each of the three basic thresholds is met, and whether all three are met overall.
Worked example — three scenarios, from a pass to a common disqualifier
A 20-year-old, 150 lb man with a hemoglobin of 14 g/dL: age passes (20 ≥ 17), weight passes (150 ≥ 110), and hemoglobin passes against the men's 13.0 g/dL threshold (14 ≥ 13.0) — all three basic thresholds are met.
A 16-year-old with the same 150 lb weight and 14 g/dL hemoglobin: weight and hemoglobin both pass, but age fails the flat 17+ cutoff this calculator uses (some states permit 16 with parental consent, not modeled here) — so overall eligibility is 0.
A 20-year-old woman weighing 100 lb with a hemoglobin of 13 g/dL: age passes, and hemoglobin comfortably clears the women's 12.5 g/dL threshold, but 100 lb falls short of the 110 lb weight minimum — so overall eligibility is 0 despite two of the three thresholds passing.
Questions
Does passing all three checks mean I'm eligible to donate blood?
Not on its own. These are three of the most basic numeric thresholds used in donor screening, but actual eligibility on donation day also depends on health history, recent travel, current medications, certain medical conditions, recent tattoos or piercings, and other factors assessed through the donor health history questionnaire — none of which this calculator evaluates. Confirm your specific eligibility with the blood bank or Red Cross directly.
Why does the hemoglobin threshold differ between men and women?
Women typically have a lower normal hemoglobin range than men. The Red Cross sets separate minimum thresholds — 12.5 g/dL for women, 13.0 g/dL for men — to keep the amount of hemoglobin and iron removed during a standard whole-blood donation within a safe margin for each group.
I'm 16 — does an ineligible age result mean I can never donate?
Not necessarily, depending on where you live. This calculator applies a flat 17-or-older cutoff, but several U.S. states allow 16-year-olds to donate with signed parental or guardian consent, and this calculator does not model that state-by-state exception. Check your state's specific rule and the collecting organization's policy.
Where do these specific thresholds come from?
The 110 lb weight minimum and the 12.5/13.0 g/dL hemoglobin thresholds are the basic eligibility criteria published by the American Red Cross for whole-blood donation. The overarching framework for donor eligibility in the U.S. is set out in FDA regulation 21 CFR 630.10.
Does the weight threshold change for younger donors?
The Red Cross applies additional height-and-weight criteria for donors 18 and younger, to keep smaller-framed younger donors from giving a disproportionate share of their blood volume. This calculator only implements the flat 110 lb adult minimum and doesn't model those additional youth-specific tables.
Is this calculator a substitute for the screening done at the donation site?
No. It checks only three numeric thresholds — age, weight, and hemoglobin. The actual screening process includes a confidential health history questionnaire, a brief physical check (blood pressure, pulse, temperature, hemoglobin), and review of eligibility criteria covering many factors this calculator does not touch.
What counts as a valid hemoglobin reading to enter here?
Use a recent hemoglobin value from a fingerstick or blood test. At an actual donation, the blood bank measures hemoglobin on-site immediately before donation, since it can fluctuate day to day — a value checked days or weeks earlier may not reflect your level on donation day.
References
- American Red Cross — Blood Donation Eligibility Requirements
- American Red Cross — Hematocrit and Hemoglobin
- 21 CFR 630.10 — General donor eligibility requirements (eCFR)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.