Nandrolone side effects are the reason the Bloodwork Bible puts Deca in the same group as trenbolone: the 19-nor steroids. That group gets special rules in my book, because 19-nors can push up prolactin and progesterone, and those two can wreck your libido. Nandrolone is an older injectable steroid, once prescribed for anemia, and it’s one of the most used steroids in bodybuilding. This page covers what it is, what the book says, the side effects from the label and the research, and the labs to run.
First, nandrolone is an anabolic steroid, usually sold as nandrolone decanoate, the “Deca” in Deca-Durabolin. It’s a long-acting injection. In the US, it was approved for anemia caused by kidney failure, because it raises red blood cells. The label now lists it as discontinued in the US [1].
Chemically, it’s testosterone without one carbon atom, which is why it’s called “19-nor.” However, that small change matters. Nandrolone turns into estrogen less than testosterone does, it acts on the progesterone receptor, and the enzyme that turns testosterone into the stronger DHT turns nandrolone into a weaker androgen instead [2][3].
The book doesn’t give Deca its own section. Instead, it treats it as part of the 19-nor family, with trenbolone and MENT, and sets three rules for that family:
The Bloodwork Bible calls prolactin “critical with 19-nor compounds” and names Deca first. When it climbs, high prolactin can cause lactation, sexual problems and trouble reaching orgasm. So the book says to test it even if you feel fine, and to add it to the mid-cycle panel whenever you run a 19-nor.
Below are the full side-effect table, the libido problem, the DHT-blocker trap, the heart data, fertility, what the medical trials show, the labs and who should never use it.
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This page documents Dr. Tony Huge’s research and self-experimentation. It is journalism and education, not medical advice, and it creates no doctor-patient relationship. Dr. Tony Huge holds a Juris Doctor; he is a lawyer, not a physician. Read the full Legal Disclaimer.