Blood donor iron levels can fall well before haemoglobin drops enough to trigger a donation deferral. That is because haemoglobin reflects the oxygen-carrying cells in your blood, while ferritin is commonly used to assess stored iron. If you donate often, a normal haemoglobin screening result does not necessarily mean your iron reserves are full.
Why Iron Stores Can Fall Before Haemoglobin
A whole-blood donation removes red blood cells and the iron they contain—about 210–240 mg of iron per donation. Your body can draw on stored iron to make new red blood cells, so ferritin may decline while haemoglobin remains within the donation service’s acceptable range. Haemoglobin screening helps check whether you meet its threshold to donate; it is not a direct test of iron stores.
In 2025, Amber Meulenbeld and colleagues analysed more than one million donation records from blood services in the Netherlands, South Africa, England and the United States. They found a consistent relationship: at low ferritin, haemoglobin recovery was linked to ferritin levels, but above a transition point that relationship disappeared. The transition differed across populations. The study supports checking ferritin as a separate measure, but it does not establish one threshold that should apply to every donor or country.
WHO May Benefit From Ferritin Testing?
Testing may be worth discussing if you donate frequently, have been deferred for low haemoglobin, or have symptoms that could fit iron deficiency. Younger donors and women—particularly those of childbearing age—are groups in whom low iron stores are more common, and frequent donation adds risk. Men can also become iron deficient; donation frequency is not the only factor.
Symptoms associated with iron deficiency include persistent fatigue, reduced exercise tolerance, restless legs, difficulty concentrating and pica—cravings for non-food substances. These symptoms have other possible causes, so they cannot confirm low iron on their own. If you have them, ask a clinician whether assessment, including ferritin testing, is appropriate. Do not assume a routine pre-donation haemoglobin check has answered that question.
What Food Can—and Cannot—Do
Iron-rich foods can contribute to your dietary iron intake and may be part of a sensible approach to maintaining it. But for many regular donors, diet alone does not replace the iron lost through repeated donations quickly or fully. Eating more iron-rich food is therefore not a reliable substitute for testing or a tailored plan if your stores are already low.
Oral iron can help restore iron stores, and research in donors shows it can improve ferritin and reduce deferrals for low haemoglobin. It can also cause effects such as constipation, nausea or diarrhoea. Do not start supplements without considering your individual circumstances: iron may be unsuitable for someone with undiagnosed iron overload, and supplementation could mask symptoms of gastrointestinal bleeding or another underlying problem. A clinician can help decide whether testing or supplementation is appropriate for you.
Blood Donor Iron Levels: Advice Varies by Region
Donation services do not all use the same approach. In the United States, the review literature describes a minimum interval of 56 days for whole-blood donation and a haemoglobin threshold of 12.5 g/dL. A study comparing services across four countries found ferritin screening in three of its four datasets, while iron supplements were advised in the US dataset and offered in South Africa. In the Netherlands, the Sanquin protocol described in a 2022 trial paper included ferritin checks for new donors and at every fifth donation, with longer deferrals for lower results.
These are examples of particular services and study settings, not a complete statement of current rules across the US, UK, EU or Australia. England also contributed data from the INTERVAL trial, whose donation schedule differed from usual NHS Blood and Transplant practice. If you donate, ask your local service what it checks, whether ferritin testing is available, and what to do if you have symptoms or a low result. Donation eligibility depends on local rules; if you have anaemia or do not meet the service’s haemoglobin threshold, you may be asked to wait.