Fluid and electrolyte disturbances: Retention of sodium, chloride, water, potassium, calcium, and inorganic phosphates.
Gastrointestinal: Nausea, cholestatic jaundice, alterations in liver function tests, rarely hepatocellular neoplasms and peliosis hepatis (see WARNINGS ).
Hematologic: Suppression of clotting factors II, V, VII, and X, bleeding in patients on concomitant anticoagulant therapy, and polycythemia.
Nervous system: Increased or decreased libido, headache, anxiety, depression, and generalized paresthesia.
Allergic: Hypersensitivity, including skin manifestations and anaphylactoid reactions.
Vascular Disorders: venous thromboembolism
Miscellaneous: Inflammation and pain at the site of intramuscular injection.
Gynocomastia is another side effect of Sustanon men suffer from. Gynocomastia is a medical condition in which men suffer from abnormally large breasts; this happens due to aromatization. Aromatization is the conversion of testosterones into estrogen. Estrogen being a female sex hormone has the ability to bind with the breast tissues and get deposited on the breasts; this causes abnormally large breasts. Although gynocomastia is not a life threatening diseases, it is quite embarrassing and in severe cases needs surgery for correction. Aromatization also causes water retention another side effect of Sustanon.
The mean oral bioavailability of finasteride is approximately 65%.  Its volume of distribution is 76 L/kg.  The plasma protein binding of finasteride is 90%.  The drug has been found to cross the blood–brain barrier , whereas levels in semen were found to be undetectable.  Finasteride is extensively metabolized in the liver , first by hydroxylation via CYP3A4 and then by aldehyde dehydrogenase .  The metabolites of finasteride have about 20% of its potency in inhibiting 5α-reductase and hence its metabolites are not particularly active.  The drug has a terminal half-life of 5 to 6 hours in adult men (18–60 years of age) and a terminal half-life of 8 hours or more in elderly men (greater than 70 years of age).  It is eliminated as its metabolites 57% in the feces and 40% in the urine .