What side effects can happen after donating blood?
Most donations go smoothly. Common side effects are mild: lightheadedness, paleness or bruising at the needle site. Serious reactions are rare and staff are trained to treat them.
Giving blood is a safe, well established procedure. As with anything that removes fluid from the body, side effects can happen, but they are usually mild and brief.
Mild reactions (most common)
- Lightheadedness and weakness: from a temporary drop in blood pressure. They pass with rest, fluids and the snack
- Paleness and cold sweats: a mild vasovagal reaction. It helps to lie down with legs raised
- Bruising at the needle site: a little blood leaks into the tissue and fades in days
- Sore arm: mild tenderness in the first hours
- Mild nausea: more common for first time donors or when nervous
Moderate reactions
- Fainting (vasovagal syncope): uncommon, more likely in first time donors or people afraid of needles. Staff are ready for it
- Larger bruise: rare, usually resolves without treatment
- Prolonged low blood pressure: treated with rest and fluids on site
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Rare reactions
- Nerve irritation: tingling or radiating arm pain, usually temporary
- Local vein clot: extremely rare
How centers prevent and treat reactions
- Screening identifies donors at higher risk
- Staff are trained to act right away
- You rest and have a snack and drink after the draw
If you feel unwell after leaving
- Lie down and raise your legs
- Drink fluids
- Do not drive if you are dizzy
- If the site bleeds, press firmly with a clean cloth for about 5 minutes and keep your arm raised
- If symptoms persist, contact the blood center, or call 911 for an emergency
This information is general and does not replace advice from a health professional. Your eligibility is always decided at the donor screening on the day of donation. Rules change, so confirm with the American Red Cross or the blood center where you plan to donate.