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Serum or plasma type (ABO blood group typing)

Published: August 9, 2026Updated: August 16, 2026

This test determines your blood type (A, B, AB, or O) and Rh factor (positive or negative) by analyzing your serum or plasma.

Quick summary

["Knowing your blood type helps with safe blood transfusions and certain medical procedures."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
73674-4
Short code
S pneum Sertyp Islt Aggl
Synonyms
S pneum Sertyp Islt Aggl
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggl
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why It Matters for You

Your blood type is determined by specific proteins (antigens) on your red blood cells. This test identifies which antigens are present, along with antibodies in your plasma that may react against them. It’s a routine check that ensures compatibility for blood donations, surgeries, or emergencies requiring transfusions.

How the Test Works

A small blood sample is taken from your arm. The lab processes it to detect the antigens (A, B, Rh) and antibodies that define your blood type. The result is typically reported as A+, B-, AB-, or O+.

Common Uses

This test is often performed during pregnancy to prevent complications like Rh incompatibility, before surgeries requiring blood transfusions, or if you’re a blood donor. It’s also used in emergencies to ensure safe blood administration.

What to Expect Before the Test

No special preparation is needed. You may have a slight bruise or pinch from the needle, but it usually fades quickly. If you’re pregnant or have a history of bleeding disorders, let your provider know.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Blood Type Check

Frequently asked questions

Why might my blood type matter in my care?
Your blood type affects compatibility for transfusions, pregnancy (e.g., Rh factor), and some medical procedures. For example, an O-negative blood type is often used in emergencies due to its universal compatibility. Your provider will use this test to tailor treatments to your needs.
What does a positive or negative Rh factor mean?
The Rh factor (positive or negative) indicates whether your red blood cells have a specific protein. If you’re Rh-negative, your body may react to Rh-positive blood during pregnancy or transfusions. This test helps prevent complications like hemolytic disease of the fetus/newborn.
Can I donate blood if I have a certain blood type?
Yes! Blood types are categorized for donation purposes. O-negative is the most needed for emergencies, while others (like AB-positive) are less common. Your provider will confirm eligibility based on your blood type and health status.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy