The blood donation eligibility checker above is deliberately not a checker in the usual sense. It does not decide anything. It takes a few answers and returns the criteria that one named blood service publishes and that your answers happen to touch, so you know which pages to read and which questions to ask before you book.
Arb Digital builds free tools that refuse to say more than they can support. Donation criteria are set by each blood service, differ between countries, and are revised as the evidence changes. Publishing a table of rules as though they were facts would be wrong on the day it was written and worse a year later.
Why This Page Gives No Verdict
Three reasons, and all of them are about you rather than about us.
First, the rules belong to the service. Every blood service sets its own criteria, and they differ substantially between countries and even between services within one country. A rule about travel, medication or a medical condition that applies in one place may not apply in another, and a web page that flattened them into one answer would be misleading wherever the reader lives.
Second, the rules change. Deferral periods are shortened and lengthened as evidence accumulates, travel rules follow disease patterns, and eligibility policies have been substantially revised in several countries in recent years. Anything published here is correct only as at the date it was checked, which for the figures on this page is 2 September 2026 against the NHS Blood and Transplant website for England.
Third, and most importantly, the service screens every donor anyway. A health check and a confidential discussion happen at every session, precisely because a form cannot see everything. A tool that told someone they were ineligible might stop a willing donor who would in fact have been welcome; one that told someone they were eligible would be making a promise it has no standing to make. Neither is acceptable, so this page does neither.
What NHS Blood and Transplant Publishes
The Who can give blood page from NHS Blood and Transplant sets out the general criteria for whole blood donation in England. As published at the time of writing, it states that donors should be generally fit and well, have suitable veins, be aged 17 to 65 if it is a first donation or up to 72 if they have donated before — and older if they donate regularly — and weigh between 7 stone 12 lb, which is 50 kg, and 25 stone, which is 158 kg.
On intervals, the same service publishes 12 weeks between whole blood donations for men and 16 weeks for women, and notes that people with genetic haemochromatosis may be able to donate as often as every 6 weeks.
Platelet donation has its own published criteria on the Become a platelet donor pages: aged 17 to 65, or up to 70 for those who have donated in the last two years, having given blood or platelets before, able to spare up to two hours, and able to travel to a platelet donor centre. Height, weight and a platelet count are checked at an assessment rather than being published as fixed thresholds, and the service states that it is safe to donate platelets as often as every two weeks although every four to eight weeks suits many people.
Every one of those figures is exposed as an editable field on this page, because the version that matters is the one the service publishes today for the country you are in.
The Formula / How It's Calculated
There is barely any arithmetic here, and that is the point. The interval calculation is weeks remaining = published interval − weeks since last donation, floored at zero.
With the defaults, that is 12 weeks published against 10 weeks elapsed, leaving 2 weeks before the published interval falls due. Set the interval to 16 weeks and the same 10 weeks elapsed leaves 6. Set it to 2 weeks for platelets and the interval has already passed.
Note carefully what that sentence says and does not say. The interval falling due is arithmetic on a number the service publishes. It is not a statement that anyone may donate on that date, because the interval is one criterion among many and the service checks the rest at the session.
The rest of the page is a lookup. Each answer maps to the published criterion it touches, and the criteria are listed for you to read. Nothing is scored, nothing is weighted, and no answer produces a pass or a fail.
The Criteria That Vary Most
Some rules are stable and easy to look up. Others are the ones that generate the most questions and change most often, and it is worth knowing which is which before you go looking.
Medication and medical conditions. The effect of a medicine on donation depends on the medicine, the reason for it and sometimes the dose, and services publish detailed lists. Many conditions and many medicines do not prevent donation at all, which is why guessing in either direction is unhelpful.
Travel. Deferral after travel depends on where, when and for how long, and follows the pattern of infections in the places concerned. These lists are updated regularly and are not stable enough to reproduce anywhere but on the service's own site.
Tattoos, piercings and acupuncture. Services publish a deferral period after these, and the period differs between services and sometimes depends on where the procedure was performed.
Pregnancy and breastfeeding. Published guidance covers how long after a pregnancy donation is possible, and services generally publish separate wording for breastfeeding.
Haemoglobin. Services set a minimum haemoglobin level and test it at the session rather than asking about it beforehand. It varies day to day, so it is not something anyone can check in advance from a web page. Our blood type calculator deals with a different topic entirely — inheritance of blood groups — and does not assess donation.
Why the Interval Exists at All
The gap between donations is not administrative. A whole blood donation removes a meaningful quantity of iron along with the red cells, and the body needs time to rebuild both. The published interval is a population-level safety margin designed so that regular donors do not become iron-depleted over time, which is also why services publish different intervals for men and women and why they check haemoglobin at every session.
Platelet donation works differently because platelets regenerate far more quickly and the red cells are returned during the procedure, which is why the published safe frequency is much shorter. The trade-off is a longer appointment and a specialist centre.
Understanding that logic is useful because it explains why intervals cannot be shortened by feeling well. Feeling fine is not evidence that iron stores have recovered, and the interval is set for the population rather than for how any individual feels on the day.
Getting the Most Out of a Session
Once you have read the criteria and booked, the practical guidance services publish is fairly consistent: eat properly beforehand, drink plenty of fluid in the hours before the appointment, avoid a very heavy workout immediately before, and tell the staff about anything that has changed since you last attended. Our water intake calculator covers general fluid intake, though the service's own advice for the day of donation takes precedence over any general figure.
Bring the details of any medication you take. Being able to name it exactly saves time and avoids a deferral that only happened because nobody could confirm what a tablet was.
And if you are deferred, ask why and for how long. Deferrals are frequently temporary and specific, and knowing the reason tells you when to come back. A deferral is not a judgement about you, and it is not permanent unless the service says so.
Arb Digital designs and builds free interactive tools that name their source, state the date the figures were checked, and hand judgement back to the organisation that actually holds it. Browse what we have already published, or tell us what your audience keeps searching for.
Browse the Free Tools Hub Talk to Arb DigitalCommon Mistakes to Avoid
- Assuming rules are the same everywhere. Every blood service sets its own criteria and they differ substantially between countries. The figures here are what one service publishes for England.
- Trusting a cached copy of a rule. Deferral periods, travel rules and medication guidance are revised. Check the service's own current pages before you book.
- Ruling yourself out without checking. Many medical conditions and many medicines do not prevent donation. Guessing in that direction loses donations the service would have welcomed.
- Treating an elapsed interval as permission. The interval is one published criterion among many, and the service screens every donor at every session.
- Expecting to check haemoglobin in advance. It varies day to day and is tested at the session. No web page can tell you what yours will be.
Related Free Tools From Arb Digital
See the blood type calculator for how blood groups are inherited, the date difference calculator and days until date calculator for working out intervals between appointment dates, the age calculator for an exact age in years, the weight converter for stones, pounds and kilograms, the water intake calculator for general hydration, and the BMI calculator for the standard height and weight index. Everything else is on the free online tools hub.
Frequently Asked Questions
No, and it never will. It lists the criteria a named blood service publishes that your answers touch. Only the service can decide, and it screens every donor at every session.
They are what NHS Blood and Transplant publishes for England, read from its own pages and checked on 2 September 2026. Other services in the UK and in other countries publish their own criteria, and every figure on this page is editable so you can substitute yours.
NHS Blood and Transplant publishes 12 weeks between whole blood donations for men and 16 weeks for women, and notes that people with genetic haemochromatosis may donate as often as every 6 weeks. Other services publish different intervals.
For whole blood in England the service publishes an age range of 17 to 65 for a first donation, up to 72 for those who have donated before and older for regular donors, and a weight range from 50 kg to 158 kg. Platelet donation has its own published wording.
Because those rules are detailed, depend on specifics such as which medicine and which country, and are revised regularly. The service's own current guidance is the only reliable source, and reproducing it here would go stale.
Not from a web page. Services set a minimum haemoglobin level and test it at the session, because it varies day to day. That test is part of the screening every donor receives.
Ask why and for how long. Deferrals are often temporary and specific, and the reason tells you when you can return. A deferral is not permanent unless the service says so.
This page is an information tool for general use only. It is not medical advice and it does not assess anyone's eligibility to donate blood, platelets or plasma. Eligibility criteria are set by each blood service, differ between countries and are revised over time. The figures quoted are what NHS Blood and Transplant published for England as read on 2 September 2026. Confirm everything with the blood service that would take your donation, and discuss any health concern with a qualified clinician.
