Viagra and kidney problems

Full question:
I would like to take Viagra but one of my kidneys is not working 100% – can I still go for  it? And how much can I take in one go?

Response from Dr Fox:
Men with kidney problems can usually take Viagra in the normal way unless they have significantly reduced kidney function. It is best if you discuss this face-to-face with a doctor who knows you, unless you are sure that you do not have significantly reduced kidney function. The maximum dose of Viagra/sildenafil is 100mg per day. See information about starting dose for Viagra. Diseases such as diabetes and kidney disease can affect hormone levels, blood circulation, and energy levels, which can contribute to erectile dysfunction.