To donate blood in the United States, you generally need to be at least 17 years old (or 16 with parental consent), weigh at least 110 pounds, and be in good health on the day of your donation. Beyond those basics, several medical, lifestyle, and travel factors determine whether you’re eligible right now or need to wait.
Age, Weight, and General Health
The baseline requirements are straightforward. You must weigh at least 110 pounds, since smaller donors face a higher risk of side effects like dizziness or fainting when a standard volume of blood is drawn. Most states set the minimum age at 17, though 16-year-olds can donate with a parent or guardian’s written consent.
Before every donation, your hemoglobin level is checked with a quick finger stick. Women need a minimum of 12.5 g/dL and men need at least 13.0 g/dL. If your level falls below that threshold, you’ll be asked to come back another day. Low hemoglobin is one of the most common reasons people are turned away at the donation site, and it doesn’t necessarily mean anything is wrong. Hydration, diet, and menstrual cycles all affect the result.
Blood Pressure, Diabetes, and Other Chronic Conditions
Having a chronic condition doesn’t automatically disqualify you. People with diabetes or prediabetes are generally eligible as long as they feel well on the day of donation, and most diabetes medications don’t cause a deferral. The same is true for high blood pressure: you can donate as long as your reading at the donation site is below 180/100. Blood pressure medications don’t disqualify you either.
Asthma is acceptable as long as you’re breathing comfortably and don’t have limitations on your daily activities. Clotting disorders like Factor V Leiden are evaluated case by case, but if you’re not taking blood thinners, you’re likely eligible. The pattern here is consistent: well-managed chronic conditions rarely prevent donation.
Medications That Require a Waiting Period
Most everyday medications, including those for blood pressure, cholesterol, thyroid conditions, and diabetes, won’t affect your eligibility. The medications that do require a deferral typically fall into a few categories.
- Blood thinners and antiplatelet drugs: Waiting periods range from 2 days to 1 month depending on the specific drug. Warfarin requires a 7-day wait, while common newer blood thinners like those prescribed for atrial fibrillation require just 2 days.
- Isotretinoin (severe acne treatment): 1-month deferral after your last dose.
- Finasteride (hair loss or prostate treatment): 1-month deferral. Dutasteride, a similar drug used for prostate symptoms, requires 6 months.
- HIV prevention medications (PrEP or PEP): 2-year deferral, whether oral or injectable.
- Certain immunosuppressants and psoriasis drugs: Deferrals range from 6 weeks to 3 years depending on the medication. One older psoriasis drug, etretinate, causes a permanent deferral because it stays in the body indefinitely.
These deferrals exist because the medications either affect the blood itself (thinners make the product unsafe for recipients) or because the underlying condition being treated poses a transmission risk that needs a window of time to rule out.
Tattoos and Piercings
In most states, a tattoo won’t delay your donation at all, provided it was done at a state-regulated facility using sterile, single-use needles and ink that isn’t reused. The same applies to cosmetic tattoos and microblading. If you got your tattoo in a state that doesn’t regulate tattoo parlors, you’ll need to wait three months.
Piercings follow the same logic. If disposable, single-use equipment was used, you’re clear to donate. If a reusable piercing gun was involved, or if you’re unsure about the equipment, the waiting period is three months.
Travel to Malaria-Risk Areas
If you’ve traveled to a region where malaria is present, you’ll need to wait 3 months after returning before you can donate. If you previously lived in a malaria-endemic area, the deferral extends to 3 years. And if you were actually diagnosed with and treated for malaria, you must wait 3 years after treatment and remain symptom-free during that time. The CDC shortened the traveler deferral from one year to three months, which means many people who were previously turned away can now donate sooner.
Pregnancy and Breastfeeding
You cannot donate blood during pregnancy. After delivery, the standard deferral period matches the length of the pregnancy, so roughly 9 months for a full-term birth. If you’re breastfeeding, the recommendation is to wait until your baby is getting most of their nutrition from solid food or formula, plus an additional 3 months. The deferral protects the parent’s iron stores, which are already heavily depleted by pregnancy and nursing.
Sexual History Screening
The FDA updated its blood donor screening guidelines to replace the old blanket deferral for men who have sex with men. The current system uses individual risk-based questions that apply equally to all donors regardless of gender or sexual orientation. These questions focus on specific recent behaviors, such as having new or multiple sexual partners, rather than categorizing donors by identity. This change brought U.S. policy in line with the scientific evidence on HIV testing windows and transmission risk.
How Often You Can Donate
The type of donation determines how long you wait before coming back. For whole blood, the standard interval is 56 days (8 weeks), which means you can donate up to six times a year. Platelet donations recover much faster, with only 7 days required between appointments. Double red cell donations, which collect twice the red blood cells in a single visit, require 112 days (16 weeks) between sessions.
These intervals exist largely because of iron. A single whole blood donation removes enough iron that your body needs 24 to 30 weeks to fully replenish its stores, even though the blood volume itself recovers within days. The Red Cross recommends taking a multivitamin with 18 mg of iron or an iron supplement for 60 days after each whole blood donation to help with recovery. For double red cell donations, they recommend 120 days of supplementation.
What Happens if You’re Deferred
Being deferred doesn’t always mean you can never donate. Most deferrals are temporary, tied to a medication, a recent tattoo, or a travel history that will eventually clear. When you arrive at a donation center, a staff member reviews your health history through a standardized questionnaire that covers all the criteria above. If something flags, they’ll tell you exactly how long to wait and when to come back. Your answers are confidential and aren’t shared with anyone outside the blood collection organization.
If you’re unsure about a specific situation, most blood centers have eligibility hotlines or online tools where you can check before scheduling an appointment. The Red Cross maintains an alphabetical eligibility list covering hundreds of conditions, medications, and circumstances.