Deca 200 is the trade name for the injectable steroid nandrolone decanoate. It was first made available as a prescription medication in 1962. Deca 200 is one of the most widely used anabolic steroids. Structurally deca 200 is very similar to testosterone, but due to chemical alterations at the 19th carbon atom, the resulting structure is a steroid that exhibits much weaker androgenic properties than testosterone.

Deca 200 is not known as a rapid muscle builder. The muscle building effect of this drug is quite noticeable, but not dramatic. The slow onset and mild properties of this steroid therefore make it more suited for cycles with a longer duration. Gains of muscle weight occur at about half the rate of that with an equal amount of testosterone. General recommendations for cycle length run from a cycle of eight weeks up to twenty weeks seems to make the most sense, specifically due to the slow, even gain of quality mass.

Although active in the body for much longer, deca 200 is usually injected once or twice per week. The average dosage for men is usually in the range of 200 to 800 mg per week. Deca 200 must be used with a testosterone base in the cycle due to the side effects associated with progesterone which are actually quite similar to those of estrogen, including negative feedback inhibition of testosterone production, enhanced rate of fat storage and possibly gynecomastia. Many believe the progestin activity of deca 200 notably contributes to suppression of testosterone synthesis, which can be marked despite a low tendency for estrogen conversion.

Side effects with deca 200 use are actually quite low. The most common complaint is excessive water retention. In off season users this can actually be a benefit, allowing the user to train heavier without concern of joint pain. Acne and gynocomastia can be of concern in higher dosages, but the most common complaint and side effect of deca 200 use is decreased sex drive.