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Anti-Globulin (Coombs) Test, Direct (IgG/IgA/IgM) - Serum

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

This test measures antibodies attached to your red blood cells, often used to diagnose conditions like autoimmune hemolytic anemia or blood transfusion reactions.

Quick summary

["Detects hidden antibodies on your red blood cells that may cause red blood cell destruction."]

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

Key facts at a glance

LOINC
22305-7
Short code
G lamblia IgA Titr Ser
Synonyms
G lamblia IgA Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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

What This Test Measures

The direct Coombs test identifies antibodies (such as IgG, IgA, or IgM) that are already bound to your red blood cells. These antibodies can trigger the immune system to attack and destroy your red blood cells prematurely, leading to anemia or other blood disorders. This test is typically performed on serum (liquid part of blood after clotting).

Why It’s Done

Your healthcare provider may order this test if you have unexplained anemia, jaundice (yellowing of skin/eyes), fatigue, or symptoms of blood breakdown. It’s also used to check for blood incompatibility before transfusions or to monitor conditions like autoimmune hemolytic anemia.

Sample Collection

A small blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum for testing. This is a quick procedure with minimal discomfort, similar to a routine blood draw.

Preparation

No special preparation is needed for this test. You may continue with your usual activities, but inform your provider if you’re taking blood-thinning medications or have a bleeding disorder.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Direct Coombs Test

Frequently asked questions

What does a positive result mean?
A positive result means antibodies are attached to your red blood cells, which can lead to red blood cell destruction. This may cause anemia or other blood-related symptoms. Your doctor will discuss next steps, such as additional tests or treatments, based on your overall health and symptoms.
Can I eat or drink before this test?
You can eat and drink normally before this test. No special fasting is required, but let your provider know if you’re taking medications that affect blood clotting.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Your healthcare provider will contact you with the results and explain what they mean for your care.
  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