Information about a laboratory test

High Prolactin (PRL): What Does It Mean?

High prolactin is physiologic in pregnancy and breastfeeding; otherwise medicines, hypothyroidism, kidney disease, or prolactinoma are possible contexts.

Test summary

Test name
Prolactin (PRL)
Abbreviations
PRL
Category
Endocrinology / Pituitary
Panel
Pituitary / Reproductive Hormones
Specimen
Serum / plasma
Common units
ng/mL, µg/L, mIU/L

What does the test measure?

Measures the blood level of prolactin, a hormone produced by the pituitary gland.

Why is the test ordered?

Used to evaluate menstrual changes, infertility, milk production outside pregnancy/breastfeeding, and some pituitary disorders.

Information about a low result

Low prolactin is generally less clinically prominent than high prolactin but may be considered in pituitary function and postpartum lactation context.

Information about a high result

High prolactin is physiologic in pregnancy and breastfeeding; otherwise medicines, hypothyroidism, kidney disease, or prolactinoma are possible contexts.

Reference and clinical context

Use the reference interval printed on your own laboratory report first. Hormone results may vary with the assay, age, sex, pregnancy, menstrual-cycle phase, and sampling time.

Reference range 1

< 20 ng/mL

Population
Adults
Sex
Male
Pregnancy status
No
Specimen
Serum / plasma

Example reference interval

This is an example interval from the cited source; it may vary by laboratory, method, and the stated clinical context.

Reference range 2

< 25 ng/mL

Population
Adults
Sex
Female
Pregnancy status
No
Specimen
Serum / plasma

Example reference interval

This is an example interval from the cited source; it may vary by laboratory, method, and the stated clinical context.

Reference range 3

< 500 ng/mL

Population
Pregnancy
Sex
Female
Pregnancy status
Yes
Specimen
Serum / plasma

Example reference interval

MedlinePlus example. Prolactin is physiologically much higher during pregnancy.

Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.

Interpretation notes

Prolactin varies during the day; sampling is often scheduled three to four hours after waking. Stress and medicines can affect results.

Related specialties

  • Endocrinology
  • Obstetrics and Gynecology
  • Urology
  • Internal Medicine

Frequently asked questions

Sources

  1. TSH (Thyroid-stimulating hormone) Test — U.S. National Library of Medicine (MedlinePlus)

    Government medical reference · 2024 · TSH purpose; high/low context; effects of age, illness and medicines · Verified: Aug 11, 2026

  2. Prolactin Levels — U.S. National Library of Medicine (MedlinePlus)

    Government medical reference · 2024 · Prolactin purpose; pregnancy, medicines and sampling-time context · Verified: Aug 11, 2026

  3. Prolactin blood test — U.S. National Library of Medicine (MedlinePlus)

    Government medical encyclopedia · 2024 · Example prolactin reference values for males, nonpregnant females and pregnancy · Verified: Aug 11, 2026

  4. Follicle-Stimulating Hormone (FSH) Levels Test — U.S. National Library of Medicine (MedlinePlus)

    Government medical reference · 2023 · FSH use with LH, estrogen, testosterone and progesterone · Verified: Aug 11, 2026

  5. Luteinizing Hormone (LH) Levels Test — U.S. National Library of Medicine (MedlinePlus)

    Government medical reference · 2023 · LH function and use with FSH and reproductive hormones · Verified: Aug 11, 2026