I dropped the dosage back down because I started to feel (what I think was) my kidneys hurt. Plus I really couldn't see any dramatic difference over the 20mgs ed. Also it gets expensive. I would recommend the 20mgs ed for 16 weeks before the 8 weeks at 40. Just my opinion. I have never heard of kidney probs. I have read anavar is the safest with benifits that go beyond muscle building, but every report I hae read were no were near the 40mgs mark. To me I feel it can be toxic if used at too high a dosage.