Blood tests for low milk supply

Should I get a blood test to see why I don’t have enough milk?

Medical tests can be useful for monitoring and diagnosing medical conditions that may affect a mother’s health and possibly her milk supply, such as thyroid problems, diabetes, or the function of the pituitary gland. Blood tests are not usually helpful in assessing breastfeeding. Successful milk production and breastfeeding depends on a number of factors, and blood tests are unlikely to capture the whole picture.

B) Why medical tests are not usually helpful to assess breastfeeding

There is no good test to measure the function of the breast (Hartman 2001). It is possible to measure levels of the hormones oxytocin and prolactin, but there is a wide range of normal levels. Also, the tests are not particularly reliable, because results depend on variety of factors including (Cox 1996; Stuebe 2015; Wagner 2018):

  • The timing of collection of the sample
  • How effectively a mother breastfeeds or expresses
  • The return of the mother’s periods
  • If a mother is taking medication, such as hormonal contraceptives, that can reduce milk supply
  • Exercise
  • Diet
  • The storage, transport, and separation of components before testing
  • The testing method
  • The values considered normal

Blood tests do not reflect anatomical causes for a low milk supply, such as insufficient glandular tissue (IGT) or breast reduction surgery.

Breastfeeding depends on a sequence of events:

When a baby does not grow well, a number of factors are generally at play and a blood test is unlikely to capture the whole picture (Wagner 2018).


Cox DB, Owens RA, Hartmann PE. Blood and milk prolactin and the rate of milk synthesis in women. Exp Physiol. 1996 Nov;81(6):1007-20
Hartmann PE, Cregan MD, Mitoulas LR. Maternal modulation of specific and non-specific immune components of colostrum and mature milk. Adv Nutr Res. 2001;10:365-87
Stuebe AM, Meltzer-Brody S, Pearson B, et al. Maternal neuroendocrine serum levels in exclusively breastfeeding mothers.. Breastfeeding Medicine. 2015;10(4):197-202
Wagner CL, Baatz JE, Newton D, et al. Analytical considerations and general diagnostic and therapeutic ramifications of milk hormones during lactation. Best Pract Res Clin Endocrinol Metab. 2018 Jan;32(1):5-16