Unfortunately, Deca Durabolin usage very commonly has the adverse side effect of interfering with recovery of natural testosterone production after a steroid cycle. Adverse side effect on libido and/or erectile function is also common, but typically only when dosage is at least 200-400 mg/week or when the drug is used alone at any effective dose. Problems are worse when Deca is not combined with testosterone or substantial doses of more androgenic compounds such as trenbolone, Masteron, or Dianabol. There is wide individual variability in response with regard to side effects on libido and erectile function. Depression of mood is also possible.