NIH Blood Bank

Iron and Blood Donation

Why Do Blood Donors Need Iron After Blood Donation?

Donating a unit of whole blood or double red cells (2-units) removes iron from your body. Frequent apheresis donations (i.e., research donors, plateletpheresis donors) also lose blood over time and can have low levels of iron. You need iron to make new red blood cells. Low levels of iron can cause anemia, which is a low hemoglobin value.

  • What is Hemoglobin?
    Hemoglobin is a protein in your blood that contains iron and gives blood its red color. Hemoglobin carries oxygen from your lungs to nourish all the tissues in your body. The NIH Blood Bank and Platelet Center check your hemoglobin level before every blood donation to ensure you meet the minimum requirements for blood donation. Female blood donors must have a hemoglobin level of at least 12.5 g/dL and male blood donors must have a hemoglobin level of at least 13.0 g/dL. If your hemoglobin is too low, you will be asked not to donate blood until your levels increase.

  • What is Iron?
    Iron is an essential mineral found in our diet and is part of hemoglobin. You need iron to make new red blood cells to replace the ones lost in a blood donation. The amount of iron you need depends on many factors, including age, gender, and how often you donate blood.

What Foods Contain Iron? 

All blood donors should add foods rich in iron and high in vitamin C to their diet. Such foods include lean meat, seafood, poultry, iron-fortified cereals, beans, lentils, tofu, and fresh spinach.

Plant-based foods such as fruits, vegetables and nuts contain iron and are a part of a nutritious well-balanced diet, but the iron contained in these foods is not absorbed as completely as the iron in meat, fish and poultry. Your body absorbs iron from plant sources better when you eat it with meat and foods that contain vitamin C, like orange juice, citrus fruits, and tomatoes.

View additional information on iron in your diet.

Who Should Take Iron Supplements After Donating Blood?

Frequent blood donors should take a multivitamin with iron in it or an iron supplement to replace the iron lost with blood donation. You are a frequent blood donor if you are:

  • A woman 18- to 50-years-old who donates 2 or more units a year
  • A woman older than 50 who donates 3 or more units a year
  • A man who donates 3 or more units a year
  • An individual who give research donations by apheresis or plateletpheresis donations on a regular basis (e.g., every month)

How Much Iron Is Needed To Replace the Iron Lost In One Whole Blood Donation?

New studies show that lower doses of iron (18 mg - 27 mg iron) that are available in multivitamins or over-the-counter iron supplements are as effective as higher doses in prescription iron (38-65 mg elemental iron) when taken for 60 days to replenish the iron lost with blood donation and are associated with fewer side effects.

It is recommended that donors take an over-the-counter multivitamin with iron or iron supplement with 18 mg or 27 mg iron (1 tablet a day for 60 days) before their next blood donation. You should discuss blood donation and any supplements that you take with your healthcare provider.

What Kinds of Iron Dietary Supplements Are Available?

  • Iron is available in many multivitamin-mineral supplements or in supplements that contain only iron. Most multivitamins for women contain iron; some multivitamins for men contain iron. Check the nutrition label for 18-27 mg iron or 38 mg iron.
  • Tablets labeled "325 mg ferrous gluconate" usually contain 38 mg of iron, which is also called "elemental iron". Please check the labeling, as indicated below.
  • If you experience side effects such as stomach upset, nausea, constipation, or other gastrointestinal symptoms, try taking a lower dose.
  • Ferrous gluconate might cause fewer side effects than ferrous sulfate
  • Always follow the directions on the package
  • Keep iron and all medications out of reach of children. Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under age 6.
  • For more information about iron supplements, see the NIH Office of Dietary Supplements website.

Reading the Labels for the Amount of Iron in One Tablet

Nutrition Facts

Serving Size 1 Tablet


Amount per serving

% Daily Value


18 mg


Nutrition Facts

Serving Size 1 Tablet


Amount per serving

% Daily Value


27 mg


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This page last updated on 11/08/2023

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