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Substance concentration in serum/plasma (e.g., protein or metabolite) measured by immunoassay

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

This test measures the amount of a specific substance in your blood, typically done to check for certain proteins, hormones, or other chemicals.

Quick summary

["This test helps diagnose or monitor conditions by identifying abnormal levels of a particular substance in your blood."]

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

Key facts at a glance

LOINC
51874-6
Short code
Num Units VZIg ordered
Synonyms
Num Units VZIg ordered
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Is Ordered

Your healthcare provider may order this test to evaluate a suspected medical condition, monitor an ongoing health issue, or check for exposure to certain substances. Common reasons include detecting infections, evaluating kidney or liver function, or assessing hormonal imbalances.

What to Expect Before the Test

You may be asked to fast for a certain period before the test, depending on the substance being measured. Avoid smoking, caffeine, or certain medications if instructed. Bring a list of medications to your appointment.

During the Test Process

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the procedure usually takes a few minutes. You can resume normal activities immediately afterward.

Possible Results and Next Steps

Results will be reviewed by your healthcare provider, who will compare them to your medical history and symptoms. If levels are outside expected ranges, further testing or follow-up may be recommended to understand the cause and guide treatment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What does an abnormal result mean?
An abnormal result doesn’t necessarily mean you have a problem right away. It may indicate that your body is producing too much or too little of the substance being tested, which can signal an underlying health issue. Your provider will discuss the findings with you and determine the next steps based on your overall health and symptoms.
How often should I get this test?
The frequency depends on your health condition and medical needs. Your healthcare provider will schedule follow-up tests based on your treatment plan and how your body responds to the test results.
Can I eat or drink anything before this test?
Follow your healthcare provider’s instructions regarding food and drink before the test. Some tests require fasting, while others may allow water or specific foods. Always confirm with them to avoid interfering with the test results.
  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