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Serum Prolactin, Monomeric

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

This test measures the amount of prolactin, a hormone produced by the pituitary gland, in your blood. Prolactin helps regulate breast milk production and affects other body functions, including hormones and reproduction.

Quick summary

["Prolactin levels can help diagnose hormonal imbalances or conditions affecting the pituitary gland."]

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

Key facts at a glance

LOINC
78994-1
Short code
Prolactin.monomeric SerPl-aCnc
Synonyms
Prolactin.monomeric SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
2
Ref high
18
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84146
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 Might This Test Be Ordered?

Your healthcare provider may recommend this test if you have symptoms like breast changes, irregular menstrual periods, infertility, headaches, or signs of a pituitary tumor. It may also be checked during pregnancy or if you’re taking certain medications that can affect prolactin levels.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if instructed. Wear comfortable clothing for blood draws. Avoid smoking or caffeine right before the test, as they can temporarily affect hormone levels.

What Happens During the Test?

A healthcare professional will insert a small needle into a vein in your arm. A small amount of blood will be drawn into a tube. The process usually takes a few minutes, and you may feel a brief pinch. The blood sample is then sent to a lab for analysis.

What to Expect After the Test

You may experience mild bruising, swelling, or soreness at the injection site. Apply gentle pressure to the area to help reduce discomfort. Rest for a short time afterward, but resume normal activities as tolerated. Contact your provider if you have severe pain, excessive bleeding, or signs of infection.

Reference range

Adult males: 2-18 ng/mL; Females: 2-29 ng/mLN/A

Specimen: serum

For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Prolactin (Serum)

Frequently asked questions

What Does This Test Tell Us?
High prolactin levels may indicate conditions like a pituitary tumor, thyroid problems, kidney disease, or certain medications (e.g., antidepressants, antipsychotics). Low levels could suggest pituitary damage, hyperprolactinemia treatments, or other hormonal imbalances. Your results will be compared to standard reference ranges for your age and sex.
How Often Should This Test Be Done?
The frequency depends on your symptoms, medical history, and treatment plan. Follow your provider’s guidance—some patients may need retests every few months or after changes in medication.
Can Diet or Lifestyle Affect Results?
Yes, certain foods, caffeine, alcohol, and stress can temporarily influence prolactin levels. Avoid smoking, caffeine, and heavy meals 24 hours before testing to get the most accurate 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