Understanding prolactin: normal levels, symptoms, and testing

Prolactin is a hormone that’s mainly known for its role in breast milk production. But did you know that prolactin also plays a role in fertility, immunity, and libido – in both men and women?

This guide will walk you through what prolactin is, why it’s important, and what a raised result could signify. 

In this article, we cover: 

• What is prolactin? 
• Why do I need a prolactin test? 
• How can I check my prolactin level? 
• What’s a normal prolactin level? 
• What are the symptoms of raised prolactin? 
• What are the causes of raised prolactin? 
• How can I lower my prolactin level? 
   

What is prolactin?

Prolactin is a hormone made by the pituitary gland in the brain. It’s mainly known for regulating milk production following childbirth, but like most hormones, it affects many systems in the body.

Normal prolactin levels are important for:

• Breast tissue development 
• Menstruation
• Fertility
• Libido
• Immunity
• The brain, and may have anti-stress effects

High levels of prolactin can also contribute to erectile dysfunction in men. 
 

Why do I need a prolactin blood test?

Your doctor may recommend a prolactin blood test if you have symptoms or conditions related to abnormal prolactin levels. 

Common reasons for testing prolactin include:

• Reproductive issues – a prolactin test can be useful for women experiencing irregular periods or fertility problems, or men with low sperm counts and erectile dysfunction.
• Pituitary disorders – if someone has symptoms of a pituitary gland tumour, such as persistent, severe headaches or visual changes, a prolactin test can help distinguish whether it may be due to a prolactinoma — a benign (noncancerous) tumour of the pituitary gland.
• Breast milk production – it’s possible for both men and women to produce breast milk abnormally, which can indicate a high level of prolactin.
• Treatment monitoring – if someone has a condition that affects their prolactin levels, they might need regular tests to make sure their treatment is effective.

How can I check my prolactin level?

You can check your prolactin level from home with our Prolactin Blood Test. Our finger-prick option means you can take the sample yourself. Our doctors will give you a personalised report on your results.
 

What is a normal prolactin level?

Normal levels of prolactin depend on your sex and whether you’re pregnant or breastfeeding. Levels can also fluctuate depending on the time of day you take the sample, stress levels, and underlying medical conditions. Your doctor will interpret your test results considering these factors and any symptoms you may have.

Normal reference ranges also vary considerably between labs. The following table is given as a guide only. 

*Note that some labs may consider results up to 700 μg/L as normal.
 

What are the symptoms of raised prolactin?

Many people with raised prolactin have no symptoms, especially if levels are only mildly raised.

Women with high prolactin may experience:

• A milky discharge from the nipples unrelated to breastfeeding (galactorrhoea)
• Absent periods (amenorrhoea)
• Infrequent periods
• A lack of ovulation and fertility problems
• Reduced bone mineral density

Men with high prolactin may experience: 

• Loss of libido
• Erectile dysfunction
• Reduced shaving frequency
• Lethargy
• Fertility problems
• Enlarged breast tissue (gynaecomastia)
• A milky discharge from the nipples (galactorrhoea)
   

What causes a high prolactin level?

A raised prolactin level affects around one in 200 adults. However, it’s 10-20 times more common in men with impotence or fertility problems, or women with absent periods [1].

There are many different causes of raised prolactin, most of which are benign. In about a third of cases of raised prolactin, there is no obvious cause.

Possible causes of raised prolactin: 

• Pregnancy and breastfeeding – prolactin increases considerably during pregnancy, peaking at delivery. Usually, levels return to baseline after about six weeks.
• Medications – many medications can increase prolactin levels, such as antidepressants, blood pressure tablets (verapamil and methyldopa), anti-sickness medications (metoclopramide and domperidone), antipsychotics (haloperidol and risperidone), and morphine [1].
• An underactive thyroid (hypothyroidism).
• Polycystic ovary syndrome (PCOS) – raised prolactin levels may be seen in around one in five women with PCOS, but levels tend to be only mildly raised.
• Cushing’s disease – Cushing’s disease is a condition caused by having too much cortisol in the body.
• Anorexia nervosa – People with anorexia nervosa try to keep their weight as low as possible by eating little or exercising too much. It can affect the balance of hormones in the body, including prolactin. 
• Chronic kidney or liver disease – around a third of people with chronic kidney disease and a fifth of people with liver cirrhosis have a mildly raised prolactin level [1].
• Drinking too much alcohol – moderate alcohol consumption is thought to increase the number of prolactin-releasing cells in the brain.
• Oestrogen – taking medications containing oestrogens can stimulate prolactin release [2].
• Testosterone – testosterone replacement therapy and anabolic steroids may raise prolactin levels.
• Supplements – supplements including red clover, fenugreek, and fennel may increase prolactin levels [3].
• Prolactinoma – a tumour of the pituitary gland in the brain can lead to excess prolactin release. Prolactinomas are more likely when prolactin levels are greater than 2000 μg/L. Results over 6000 μg/L are usually due to a large prolactinoma (macroprolactinoma) [4].

When taking a prolactin test, other physiological factors can also cause a raised result. In these cases, it’s best to repeat the test, avoiding the potential cause.

The following factors may also affect your prolactin result: 

• Stress – acute stress increases prolactin levels by varying amounts [5]. It’s best to take your test when you are feeling as relaxed as possible. 
• Nipple stimulation – any form of nipple stimulation, and particularly breastfeeding, can cause prolactin levels to increase [6]. 
• Sexual intercourse – prolactin levels surge after orgasm, so it’s best to avoid sex or masturbation before taking a prolactin test. Prolactin levels can increase up to fivefold for at least 60 minutes following orgasm, and may even continue to be raised into the following day [7].
• Timing –sleep increases prolactin levels, so levels tend to peak between 4 and 7am. Taking your sample midmorning, at least an hour after waking, is more likely to return a normal result. Levels trough in the evening [8].
• Eating – generally, it’s not necessary to fast before a prolactin test, as food has only a very small effect on prolactin levels. But if the prolactin result is slightly raised, it should be repeated as a fasting sample [9].
   

How can I lower my prolactin level?

Maintaining normal prolactin levels is important for hormonal balance and overall health. Usually, addressing the underlying cause is the first step. For example, medications are common culprits and should be reviewed with your doctor. Prolactinomas, on the other hand, are treated with medicines, radiation, or surgically removed. 

If causes like these have been excluded, there may be ways you can naturally lower your result. 

Ways to lower prolactin levels naturally: 

• Reduce stress – find out our top 10 ways you can de-stress.
• Reduce high-intensity workouts – it's important to make sure you incorporate adequate rest periods.
• Include vitamin B6 in your diet – vitamin B6 is a natural prolactin inhibitor that is likely to reduce your levels [10,11].
• Reduce your alcohol intake – drinking too much alcohol disrupts the hormonal system in the body and can increase prolactin levels [12].
• Discuss your medications and supplements with your doctor – if you can safely stop prolactin-raising medications, it’s likely to reduce your levels.

If the cause of your raised prolactin isn’t found, but it causes ongoing problems, your doctor may consider medications such as dopamine agonists to your lower prolactin level. 
 

What should I do if my prolactin is raised? 

Modest rises in prolactin (up to 1000 μg/L) are often nothing to worry about and are usually due to things like stress, recent intercourse, heavy exercise, or medications. In these cases, your doctor might advise repeating the test in four to six weeks.

If your prolactin level remains consistently raised or is very high, you may need further tests to find out the underlying cause. If you’re concerned, it’s best to speak to your GP. 

References

1. Assessment of hyperprolactinaemia. BMJ Best Practice; 2022. Available: https://bestpractice.bmj.com/topics/en-gb/538
2. Torre DL, Falorni A. Pharmacological causes of hyperprolactinemia. Ther Clin Risk Manag. 2007;3: 929–951.
3. Sevrin T, Boquien C-Y, Gandon A, Grit I, de Coppet P, Darmaun D, et al. Fenugreek Stimulates the Expression of Genes Involved in Milk Synthesis and Milk Flow through Modulation of Insulin/GH/IGF-1 Axis and Oxytocin Secretion. Genes (Basel). 2020;11: 1208. doi:10.3390/genes11101208
4. Test and Tubes. [cited 4 Jan 2024]. Available: https://www.leedsth.nhs.uk/a-z-of-services/pathology/test-and-tubes/blood-sciences/prolactin
5. Lennartsson A-K, Jonsdottir IH. Prolactin in response to acute psychosocial stress in healthy men and women. Psychoneuroendocrinology. 2011;36: 1530–1539. doi:10.1016/j.psyneuen.2011.04.007
6. Levin R, Meston C. Nipple/Breast Stimulation and Sexual Arousal in Young Men and Women. The Journal of Sexual Medicine. 2006;3: 450–454. doi:10.1111/j.1743-6109.2006.00230.x
7. Leeners B, Kruger THC, Brody S, Schmidlin S, Naegeli E, Egli M. The Quality of Sexual Experience in Women Correlates with Post‐Orgasmic Prolactin Surges: Results from an Experimental Prototype Study. The Journal of Sexual Medicine. 2013;10: 1313–1319. doi:10.1111/jsm.12097
8. Basir HRG, Razavi Z, Chehreghani M, Karami M, Dehghan A. Is Morning Prolactin Level Sufficient for Diagnosis of Mild Hyperprolactinemia? J Kermanshah Univ Med Sci. 2019;23. doi:10.5812/jkums.86003
9. Causes of hyperprolactinemia - UpToDate. [cited 3 Jan 2024]. Available: https://www.uptodate.com/contents/causes-of-hyperprolactinemia
10. Moretti C, Fabbri A, Gnessi L, Bonifacio V, Fraioli F, Isidori A. Pyridoxine (B6) suppresses the rise in prolactin and increases the rise in growth hormone induced by exercise. N Engl J Med. 1982;307: 444–445. doi:10.1056/NEJM198208123070719
11. Zhuo C, Xu Y, Wang H, Fang T, Chen J, Zhou C, et al. Safety and Efficacy of High-Dose Vitamin B6 as an Adjunctive Treatment for Antipsychotic-Induced Hyperprolactinemia in Male Patients WithTreatment-Resistant Schizophrenia. Front Psychiatry. 2021;12: 681418. doi:10.3389/fpsyt.2021.681418
12. Rachdaoui N, Sarkar DK. Pathophysiology of the Effects of Alcohol Abuse on the Endocrine System. Alcohol Res. 2017;38: 255–276.