Most healthy adults can donate blood, but a surprisingly long list of factors can make you temporarily or permanently ineligible. These range from basic requirements like age and weight to medical history, medications, travel, and sexual activity. Some disqualifications last a few weeks, others are lifelong.
Basic Age and Weight Requirements
You must be at least 17 years old to donate blood in most states, though 16-year-olds can donate with parental consent. There’s no official upper age limit at most blood banks as long as you’re in good health. You also need to weigh at least 110 pounds. Height and weight requirements can vary depending on the type of donation: whole blood, platelets, double red cells, or plasma each have slightly different thresholds because of how much blood volume is drawn.
Low Iron and Hemoglobin Levels
Before every donation, your hemoglobin is checked with a quick finger prick. Women need a minimum level of 12.5 g/dL, and men need at least 13.0 g/dL. If you fall below these cutoffs, you’ll be turned away that day to protect you from becoming anemic. This is one of the most common reasons people are deferred, especially women who menstruate, vegetarians, and frequent donors. Eating iron-rich foods or taking a supplement in the weeks before your appointment can help.
Conditions That Permanently Disqualify You
Some medical histories result in a lifelong ban from donating. These include:
- HIV infection: Anyone who has tested positive for HIV or has ever taken antiretroviral therapy is permanently deferred, regardless of viral load or treatment success.
- Creutzfeldt-Jakob disease (CJD) risk: If you’ve received a transplant of dura mater (a tissue covering the brain) from a deceased donor, you’re permanently ineligible because of the risk of transmitting this rare, fatal brain disease. The same applies if you’ve been diagnosed with or are at genetic risk for CJD.
- Xenotransplantation: Anyone who has received an organ or tissue from an animal is indefinitely deferred.
- Hemophilia or clotting factor deficiencies: People with these conditions are indefinitely deferred for their own safety, since donating could put them at risk of bleeding complications.
Hepatitis B and hepatitis C infections also lead to permanent deferral at most blood collection centers, as do certain other chronic bloodborne infections. A positive test for Babesia, a tick-borne parasite, results in a deferral of at least two years from the most recent reactive test.
Cancer History
A cancer diagnosis doesn’t always mean you can never donate again, but the wait time depends on the type and severity. Common, slow-growing skin cancers like basal cell carcinoma and squamous cell carcinoma of the skin only require a four-week deferral after surgical removal. More serious cancers, including breast, prostate, colon cancer, and melanoma, require you to wait at least one year after completing treatment. Blood cancers like leukemia and lymphoma typically result in a permanent deferral because of the nature of the disease.
Medications That Delay Donation
Many medications don’t affect your eligibility at all, but a few require a waiting period. The concern isn’t usually about the drug harming the blood recipient. It’s often about the underlying condition being treated or, in some cases, the drug’s potential to cause birth defects if transfused to a pregnant person.
- Isotretinoin (acne medication): 1-month wait after your last dose
- Finasteride (used for hair loss or prostate issues): 6-month wait
- Blood thinners: 7-day wait for most anticoagulants, including common ones prescribed for blood clots or atrial fibrillation
Aspirin doesn’t disqualify you from whole blood donation, though it may affect platelet donation. Antibiotics typically require that you finish your course and feel well, since it’s the active infection that’s the real issue. If you take insulin, blood pressure medication, or antidepressants, you can generally still donate.
Sexual Activity and the New Risk-Based Screening
The FDA overhauled its blood donation screening in 2023, dropping the long-standing policy that specifically deferred men who have sex with men. The new approach applies the same questions to every donor regardless of sex or sexual orientation.
Under the current guidelines, all donors are asked whether they’ve had a new sexual partner or more than one sexual partner in the past three months. If you answer yes to either, you’re then asked whether you’ve had anal sex in that same timeframe. If you have, you’re deferred for three months from your most recent sexual contact. This applies equally to everyone. People who take pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) for HIV prevention are also deferred for three months after their last dose.
Travel to Malaria-Risk Areas
If you’ve traveled to a region where malaria is common, you’ll need to wait three months after returning before you can donate. This was recently shortened from a full year. If you previously lived in a malaria-endemic area rather than just visiting, the wait is longer: three years. These deferrals exist because malaria can linger in the bloodstream without causing obvious symptoms, and standard blood screening doesn’t always catch it.
Tattoos and Piercings
Getting a tattoo at a state-regulated shop that uses sterile, single-use needles and fresh ink generally won’t affect your eligibility at all. But if your tattoo was done in a state that doesn’t regulate tattoo facilities, you’ll need to wait three months. The same logic applies to piercings: if the equipment was single-use and disposable, you’re fine. If a reusable piercing gun was involved, or if there’s any doubt about whether the instruments were disposable, you’ll wait three months.
Pregnancy and Breastfeeding
You cannot donate blood while pregnant. After delivery, the WHO recommends waiting at least as many months as the pregnancy lasted, which means roughly nine months for a full-term pregnancy. If you’re breastfeeding, the deferral extends until three months after your baby is mostly weaned and getting nutrition primarily from solid food or formula. These waiting periods give your body time to rebuild its own blood volume and iron stores.
Recent Vaccines
Most vaccines, including the flu shot and standard mRNA or inactivated COVID-19 vaccines, require no waiting period at all. You can donate as soon as you feel well. Live-attenuated vaccines are the exception. These use a weakened form of the actual virus, and in the U.S., the FDA recommends waiting 14 days after receiving one. Examples include the MMR vaccine, chickenpox vaccine, and certain types of COVID-19 vaccines used outside the U.S. that are based on live viral vectors.
Other Common Reasons for Temporary Deferral
A handful of everyday situations can also postpone your donation. If you have a cold, flu, or other active infection, most blood banks will ask you to come back when you feel better. A fever on the day of your appointment disqualifies you. If you’ve received a blood transfusion yourself, you’ll typically wait three months. Dental work involving major procedures may require a short deferral, usually a day or so for routine cleanings and up to three days for extractions or root canals, depending on the blood bank’s policy.
If you’ve been told you can’t donate and aren’t sure why, the screening staff at your local blood center can walk you through exactly which deferral applies and how long it lasts. Many deferrals that used to be permanent have been shortened in recent years as testing technology has improved.