Can a woman lactate when not pregnant?

When having a hot bath recently, white liquid was present on my nipples. I squeezed my breast gently and found that I could extract a fair amount of what appeared to be milk. Worrying that I was pregnant, I took two pregnancy tests, but both were negative.

Sunday, March 09, 2014

Dear Doctor;

When having a hot bath recently, white liquid was present on my nipples. I squeezed my breast gently and found that I could extract a fair amount of what appeared to be milk. Worrying that I was pregnant, I took two pregnancy tests, but both were negative. I take Depo-Provera, which stops my periods, so I have no other way of monitoring this possibility. Is it possible to lactate if you are not pregnant? Could this be a side-effect of my contraceptive?

Joys, 26. 

Dear Joys,

Lactation without pregnancy, also called galactorrhoea, is indeed worrisome. You have not specified whether it has happened one or two times or is present regularly. High levels of prolactin, estrogen and progesterone can result in production of milk from mammary glands though one may not be pregnant. Hormonal disorders like hypothyroidism, tumors like those of pitituitary, prolactinoma, etc, can also lead to this condition. Some drugs like those used for gastritis, high blood pressure, among others, cause galactorrhoea as adverse effect. In your case, it could be due to the hormonal contraceptive depo provera. 

If possible, do tests to exclude hormonal disorders. Try using alternate methods of contraception. Treatment of abnormal lactation usually depends on treating the cause.