Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.
What the test is
It's needed before transfusions and early in pregnancy. Rh-negative pregnant people may need an Rh immune globulin shot.
Why it's done
- Before surgery or a transfusion
- Early pregnancy
- Blood or organ donation
Getting ready and what happens
- No special preparation is needed.
How the test is done
- A health worker cleans the skin, puts a band around your arm, and draws blood from a vein with a small needle. It takes a few minutes.
What the results mean
Your type
Reported as A, B, AB, or O and positive or negative. O negative is the universal donor for red cells; AB positive can receive from all types.
Rh negative in pregnancy
You'll likely get a shot around 28 weeks and after delivery to protect future pregnancies.
Questions to ask your provider
- What do my results mean for me?
- Do I need to repeat this test or have other tests?
Risks
A blood draw is very safe. You may have slight pain or a small bruise where the needle went in.
Related conditions
Related tests
Sources
Last updated 2026-11-13.