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Understanding Your Diagnostic Lab Test: What It Is, Why Your Doctor Ordered It, and What to Expect

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

This test checks for abnormal levels or presence of monocytes, a type of white blood cell, in your blood sample.

Quick summary

{"Monocytes are white blood cells that help your body fight infections","Abnormal results may indicate infection, inflammation, or blood disorders","The test uses a small blood sample taken from your arm","Your doctor will interpret results based on your overall health condition"}

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

Key facts at a glance

LOINC
30441-0
Short code
MONO
Synonyms
Abn Monocytes NFr Bld
Category
chemistry
Sample
whole-blood
Container
K2-EDTA (lavender/purple top) vacuum tube
Units
N/A
Ref low
0.2
Ref high
1
Critical range
0.05 N/A – 2 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Automated flow cytometry or impedance analysis with manual microscopy confirmation of abnormal results
CPT
85004
SNOMED
59408007
Specimen volume
3-5 mL whole blood
Stability
Room temperature (18-25°C): 24-48 hours; Refrigerated (2-8°C): up to 72 hours. Do not freeze.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
1–6 hours
Order
routine

What is this test and what does it actually measure in my body?

The Monocytes Abnormal/Leukocytes in Blood test measures the number or characteristics of monocytes in your bloodstream. Monocytes are a type of white blood cell (leukocyte) that plays a crucial role in your immune system. They help protect your body by engulfing (phagocytosing) foreign particles, dead cells, and microorganisms, and they also help coordinate immune responses.

Why is this test performed and when might my doctor recommend it for me?

Your doctor may order this test to: (1) check for infections such as viral, bacterial, or parasitic infections, (2) evaluate inflammatory conditions like rheumatoid arthritis or lupus, (3) diagnose blood disorders including leukemia or myeloproliferative neoplasms, (4) monitor response to treatment for certain conditions, or (5) investigate unexplained symptoms like fever, fatigue, or persistent infections.

How is the test done, how should I prepare, and what can I expect during the procedure?

A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where it is analyzed using automated blood analyzers to count and examine the white blood cells, specifically focusing on monocytes. The procedure typically takes only a few minutes and requires no special preparation.

Reference range

Absolute: 0.20-1.00 x10^9/L; Relative: 2-10% of total leukocytesN/A

Specimen: whole-blood

No special preparation required. Avoid strenuous exercise before collection as this may temporarily alter WBC counts. Inform laboratory of current medications, especially corticosteroids, which can affect monocyte counts.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated monocyte levels (monocytosis) may indicate: chronic infections (such as tuberculosis), inflammatory disorders (like rheumatoid arthritis, Crohn's disease), certain cancers (particularly blood cancers like chronic myelomonocytic leukemia), or recovery from acute infection. Low monocyte levels (monocytopenia) may be seen with HIV/AIDS, certain bone marrow disorders, or during chemotherapy treatment. Your doctor will consider these results alongside other blood tests and your clinical symptoms to make an accurate diagnosis.

Frequently asked questions

Do I need to fast before this test?
Generally, no fasting is required for this test. However, always follow your doctor's specific instructions if they give you any special preparation guidelines.
Is this test painful?
You may feel a brief prick or sting when the needle is inserted to draw blood. This is generally well-tolerated and the discomfort is minimal and short-lived.
What do abnormal results mean?
Abnormal monocyte results do not always indicate a serious condition. Your doctor will interpret the results in context with other blood findings, your medical history, and current symptoms. Further testing may be needed to determine the exact cause.
How long does it take to get results?
Results are typically available within a few hours to one day, depending on the laboratory. Your healthcare provider will contact you with the results or discuss them at your follow-up appointment.
  1. 1
    MedlinePlus - MonocytesSource
  2. 2
    Mayo Clinic - Complete Blood Count (CBC)Source

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