Common side effects include nausea, headache, altered libido, fluid retention and premature cessation of growth in adolescents. In women it may also cause menstrual irregularities and increased body hair, and in men infertility, impotence, shrinking of testes and breast enlargement are possible. Liver damage and jaundice is a rare complication.
Methenolone interacts with anticoagulants (eg. warfarin), corticosteroids, insulin, hypoglycaemics and echinacea.
Although it does not cause dependence or addiction, short term gains in muscle bulk when used inappropriately by body builders, may result in long term permanent body damage that may lead to early heart attacks, infertility, bone weakness, liver disease and premature death. Bottom line is – don’t use it except under strict medical supervision when indicated for specific diseases.