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Cow Milk IgG Radioallergosorbent Test (RAST), Qualitative (Deprecated)

Published: August 9, 2026Updated: August 17, 2026

A blood test that detects cow's milk-specific IgG antibodies. It may support evaluation of suspected milk sensitivity but does not by itself diagnose milk allergy.

Quick summary

["A positive result suggests cow's milk-specific IgG antibodies, but it does not confirm an allergy or intolerance."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
21230-8
Short code
Deprecated Cow Milk IgG RAST Ql
Synonyms
Deprecated Cow Milk IgG RAST Ql
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
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 is this test?

This qualitative laboratory test looks for IgG antibodies directed against cow's milk proteins in a blood sample. The RAST name refers to an older type of allergen-antibody testing, and this test designation is deprecated.

Why might I need this test?

A clinician may order this test as part of an evaluation of gastrointestinal symptoms or other complaints thought to be related to cow's milk. It may also be used for dietary guidance, but results should be interpreted alongside the medical history and other allergy testing.

How is the test performed?

A blood sample is tested using a RAST-type immunoassay to determine whether cow's milk-specific IgG is present. Because the test is qualitative, the result is generally reported as positive or negative rather than as a measured concentration.

How do I prepare for the test?

Special preparation is usually not required. Follow the laboratory's instructions, and tell the clinician if you have recently changed your diet, started new medicines, or had another allergy test.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Cow Milk IgG RAST

Frequently asked questions

Does a positive result mean I am allergic to cow's milk?
No. Cow's milk-specific IgG can occur in people who tolerate milk and does not by itself confirm an allergy. Your clinician should interpret the result with your symptoms, history, and any other appropriate testing.
Is this the same as a cow's milk IgE test?
No. This test detects IgG antibodies, while an IgE test looks for the type of antibody more closely associated with immediate allergic reactions. The two results have different clinical meanings.
Why is the test listed as deprecated?
The test designation is no longer current, which may mean that a newer laboratory method or clinical testing strategy is preferred. Ask the ordering clinician whether an updated or alternative test is appropriate.
  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 17, 2026. · Read our editorial policy