Actually that is how it works. Many steroids stay in the blood months after.
2 – 4 months
Testosterone Cypionate, Primoteston Depot, Sten, Sustanon, Sostenon, Durateston, Anadrol, Anapolin, Hemogenin, Stenox, Halotesten, and Winstrol are drugs, which can show up on a blood or urine screen within one to four months of use. These are acceptable for off-season use by many athletes who are not tested during this period, as they are often out of the system by the time the season starts.
2 to 6 weeks
Nilevar, Parabolan, Dianabol (oral), D-Bol (oral), Primobolan Depot, Anavar, Winstrol/Stanozolol (oral), and testosterone Propionate are compounds, which work fast and move through the system very quickly. Just as their half-life is short, the positive anabolic effects upon their body are done quickly as well.