You should take Anastrozole during the whole period of a steroid cycle to mitigate possible side effects of aromatization. For example, when using testosterone propionate, anastrozole must be taken up to the fifth day after the last injection. And after long estered testosterones (enanthate, decanoate, cypionate, Sustanon, etc.), anastrozole has to be taken up until the third week after the last injection, and sometimes longer.
If you are on steroids with a short half-life (methandrostenolone), anastrozole can be taken with a lower dosage and frequency (0.5 mg 3 times a week or every other day). After 15-20 days of administration, you can repeat your blood checks.
When using testosterone propionate, for example, 100 mg. / every other day, the dosage of anastrozole can be 0.5 mg every other day, or every day 0.5 mg, or 1 mg every day, and the last intake of anastrozole should be on the fifth day after the last injections.