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An important consideration when planning a steroid cycle, in particular the timing of dosing to be administered, is the active half-life of the drug being employed... The half-life may be defined as the time (t) the level is half of the starting level of a given compound; at time 2t, the level is a quarter of the starting level, and at time 3t, the level is an eighth of the starting level, and so on. This information is vital in the timing of the dosing when attempting to achieve a more stable blood concentration, which leads to greater overall results and maintenance of gains... Some fluctuations of concentration levels are acceptable, and are also mostly unavoidable, but should be kept to a minimum. This post covers the half-life's of the most commonly used steroids, esters and ancillary compounds. Oral steroids Drug Active half-life Anadrol / Anapolan50 (oxymetholone) 8 to 9 hours Anavar (oxandrolone) 9 hours Dianabol (methandrostenolone, methandienone) 4.5 to 6 hours Methyltestosterone 4 days Winstrol (stanozolol) (tablets or depot taken orally) 9 hours Depot steroids Drug Active half-life Deca-durabolin (Nandrolone decanate) 15 days Equipoise 14 days Finaject (trenbolone acetate) 3 days Primobolan (methenolone enanthate) 10.5 days Sustanon or Omnadren 15 to 18 days Testosterone Cypionate 12 days Testosterone Enanthate 10.5 days Testosterone Propionate 4.5 days Testosterone Suspension 1 day * Winstrol (stanozolol) 1 day *Winstrol depot does not actually possess a classical half-life because it is un-esterified... Instead, the microcrystals dissolve slowly... Once they have all dissolved levels of the drug fall very rapidly... It is still an important consideration, and we have included it with a half-life of one day. .. Steroid esters Drug Active half-life Formate 1.5 days Acetate 3 days Propionate 4.5 days Phenylpropionate 4.5 days Butyrate 6 days Valerate 7.5 days Hexanoate 9 days Caproate 9 days Isocaproate 9 days Heptanoate 10.5 days Enanthate 10.5 days Octanoate 12 days Cypionate 12 days Nonanoate 13.5 days Decanoate 15 days Undecanoate 16.5 days Ancillaries Drug Active half-life Arimidex 3 days Clenbuterol 1.5 days Clomid 5 days Cytadren 6 hours Ephedrine 6 hours T3 10 hours A practical example is if one was to inject 100mg of testosterone propionate and allow blood levels to peak... In 4.5 days time (half-life duration from the above tables) and providing no other injections had taken place, the level would be reduced to 50mg... Again, a further 4.5 days down the line and levels would have dropped to 25mg, and the value keeps halving every 4.5 days.