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A great many people never donate blood because they assume their tablets rule it out anyway. Usually that is not the case: well-controlled high blood pressure, thyroid hormones or an allergy medicine are as a rule not grounds for exclusion. What matters is often not the substance but the condition behind it — and the question of whether your blood could harm someone else. What you should never do: stop a medicine in order to be allowed to donate.
At the donation appointment every line counts — including the vitamin tablet. brite keeps it all in one place.
People who take something regularly often strike blood donation off their list from the outset. Yet for a large part of long-term medication the following holds: it does not stand in the way of donating, as long as the underlying condition is stable and you feel well. German donation services work to the Richtlinie Hämotherapie, the haemotherapy guideline issued by the German Medical Association (Bundesärztekammer) — and for many groups of substances that guideline simply provides for no deferral at all.¹ Typical examples:
Deferral periods seem arbitrary as long as you do not know their purpose. In fact they follow three perfectly understandable ideas.
Whatever is circulating in your blood ends up in the blood product — a substance does not vanish during processing. The person receiving that unit may be a premature baby, a woman who has haemorrhaged in childbirth or someone with a severely weakened immune system — and they cannot decide whether they want your medicine along with it. So the guideline decides on their behalf, and it does so cautiously.
Donating whole blood means losing a considerable volume in a short time. If you are prone to low blood pressure, take a diuretic or are treated with an anticoagulant, you carry a higher risk of circulatory problems or of the puncture site bleeding afterwards.
This is the point most often misunderstood. Very often it is not the substance that is the problem but the diagnosis it was prescribed for. An anticoagulant does not exclude you because the molecule itself is dangerous, but because there is almost always a cardiovascular condition behind it. That is why the question on the screening questionnaire is never only "Which medicine?" but always also "What for?".
The table below shows the pattern, not the binding period. The specific time frames are set by each donation service on the basis of the haemotherapy guideline and the relevant product information.
| Substance / situation | What it is about | What generally applies |
|---|---|---|
| Blood pressure medicines with stable readings | nothing relevant is transmitted | Donation usually possible; the reading on the day decides |
| Thyroid hormones | replacement of the body's own hormone | Donation usually possible at a stable dose |
| Antihistamines, hormonal contraception | no relevant transmission | Donation usually possible if there is no acute infection |
| Antibiotics | acute infection plus the substance in the blood | Deferral until the infection has cleared and for a set period beyond that |
| Aspirin and other NSAIDs | they inhibit platelet function | Whole blood donation usually possible; for platelet donation a deferral of days |
| Isotretinoin, finasteride, dutasteride | potential to harm an unborn child | Deferral from the last dose, weeks to months depending on the substance |
| Vaccination with an inactivated vaccine | no replicating pathogens | Frequently no deferral, or a very short one, if you have no symptoms |
| Vaccination with a live vaccine | attenuated but replicating pathogens | Deferral over several weeks |
| Oral anticoagulants as long-term therapy | bleeding risk and underlying condition | As a rule exclusion from donating |
| Immunosuppressants, cytotoxic drugs | underlying condition and substance profile | Deferral or exclusion, always assessed case by case |
Two reasons interlock here. First, the substance is circulating in your blood and would be transmitted with the donation — no small matter if the recipient is allergic to antibiotics. Second, and this weighs more heavily: anyone who needs an antibiotic has a bacterial infection. Pathogens in the blood are the reason donation criteria exist at all.
So it is not enough to have swallowed the last tablet. The usual arrangement is a deferral that begins only after the infection has fully cleared — that is, once you are free of fever and symptoms — and then runs on for a set period.
A special case is long-term, low-dose antibiotic treatment, for instance for acne: here there is no acute infection, and the assessment sometimes turns out differently — a case-by-case decision at the donation centre. Conversely, a cold with fever or a gastrointestinal infection without any antibiotic also means postponing.
This is worth looking at closely, because it involves two completely different situations with the same substance.
Aspirin and ibuprofen inhibit the function of the blood platelets. With aspirin this inhibition is particularly stubborn: the substance blocks an enzyme in the platelets permanently, and because platelets have no cell nucleus they cannot make it again — function only returns with newly formed platelets. With ibuprofen, by contrast, the inhibition is reversible and considerably shorter.
For whole blood donation this usually makes no difference. For platelet donation it is central: a product made from platelets whose function is inhibited does not do its job. So a deferral of a few days applies here, and it is longer for aspirin than for other painkillers. Your donation service will tell you which period applies; a comparison of the substances is in the guide Painkillers compared.
Low-dose aspirin as long-term therapy after a heart attack or a vascular procedure is something else entirely. Here the sticking point is not the tablet but the cardiovascular condition behind it — and that as a rule leads to exclusion.
brite records every dose — which makes answering the questionnaire easy.
This is the classic among the long deferral periods — and the one fewest people have on their radar, because both substances are often taken by young, healthy men. Isotretinoin is prescribed for severe acne, finasteride for benign enlargement of the prostate and for hereditary hair loss. Both are considered teratogenic — they can harm the development of an unborn child; for isotretinoin there is therefore a strictly regulated pregnancy prevention programme.
And that closes the circle back to blood donation: a unit of blood can reach a pregnant woman, for instance after heavy bleeding during childbirth. Donating is therefore ruled out while you are taking the medicine and blocked for a set period afterwards. How long that period is depends on how long the substance takes to be eliminated — considerably longer for dutasteride than for finasteride.
Vaccinations are not grounds for exclusion, but they are a reason to plan the appointment:
Which vaccinations are due in adulthood is set out in the guide Vaccinations for adults. It is practical to space your donation and vaccination appointments deliberately apart.
Here the answer is clearer than for almost anything else: if you are permanently anticoagulated, you cannot as a rule donate blood. That applies to vitamin K antagonists such as phenprocoumon just as much as to the direct oral anticoagulants such as rivaroxaban or apixaban, and equally to antiplatelet drugs such as clopidogrel.
There are two reasons for this. First, your own risk: the puncture site can bleed more easily afterwards, and a circulatory collapse is more awkward to manage under anticoagulation. Second, the underlying condition: behind long-term therapy there is almost always atrial fibrillation, a previous thrombosis or a prosthetic heart valve — situations in which donating is advised against in any case. Everything about daily life with these substances is in the guide Living with blood thinners and, if an operation is coming up, in Medications before surgery.
It sounds pragmatic: pause the tablet for a week, go and donate, then carry on. That is precisely the most dangerous thought in this article.
And the donation service does not want that anyway: donating is voluntary, your treatment is not. Pausing therapy in secret undermines exactly the safety check the interview is there for. If donating matters to you, raise it at your next appointment at the practice.
Before every donation you fill in a detailed questionnaire and then speak to a doctor. That is the real safety check of the whole system — and it only works if what you report is complete. Experience shows the same things get left out:
A deferral, incidentally, is not a verdict on you — it only means this appointment does not fit. The basics of handling your own medication are in How to take medications correctly.
Substance, dose, reason for taking it — brite shows the doctor the full picture in seconds.
Before every donation your haemoglobin is measured, usually from a drop of blood from your fingertip. The usual minimum values are 12.5 g/dl for women and 13.5 g/dl for men; anyone below that is deferred.² That is not red tape but protection against causing your own anaemia.
Because every whole blood donation takes iron out of the body — it sits in the haemoglobin and goes with the unit. That is why the intervals between donations are regulated: there are usually at least eight weeks between two whole blood donations, and up to four donations a year are provided for in the case of women and up to six in the case of men.² If you donate regularly and also have heavy periods, you can slip quickly into iron deficiency — right through to iron deficiency anaemia. The first warning sign is usually persistent fatigue. At that point your ferritin should be measured rather than going through with the next appointment.
You know the usual advice: stay lying down until you feel stable, drink plenty, avoid alcohol, the sauna and intense exercise. For people on long-term medication, two points are added:
A case of its own is diabetes: whether donating is possible depends on the form of treatment and your metabolic situation and is assessed individually; anyone using insulin is as a rule excluded in Germany. That too is expressly a medical decision, not a self-assessment.
Digital medication plan
All your preparations in one place — including over-the-counter products and supplements, which otherwise go missing from the donation questionnaire time and again.
Health history
Records when a course of treatment ended — exactly the detail that counts for deferral periods.
Medication reminder
Keeps your rhythm steady even on a day with a donation appointment — no missed dose just because the routine is unfamiliar.
Interaction check
Shows critical combinations before they become a problem — iron supplements, for instance, alongside substances whose absorption they interfere with.
