That was what my uro did.

I suspect that if your PSA failed to reach zero at one month,
the doc would say, Let's wait at least until month 3 to be sure.

   Alan

One study suggests that PSA decays with a half-life of 2.7 days
(actually the decay prosess is biphasic, but let's keep it simple),
other studies suggest shorter times, but 2.7 days will provide a "worst
case" estimate   After 1 half-life, only 50% of the original PSA is
left, after 2 half-lives, only 25% is left, and so on.  It is typically
assumed that after 10 half-lives whatever is decaying (PSA,
radioisotope, etc.) is gone; only 0.1% of the original amount would
remain.  Now remember that during the operation, a lot of extra PSA was
dumped into the blood stream.  Say going in your PSA was 6.0 ng/ml and
immediately following surgery it was 12 (just a wild guess on my part).
So in the case at hand we could expect the PSA after 10 half-lives or
27 days post surgery, to be 0.001 x 12 = 0.012 ng/ml.  The PSA would be
detectable with some ultrasensitve tests.  So most docs will wait 2-3
months prior to taking the first PSA reading.  No point in rushing
things and getting a detectable reading.  After 20-30 half-lives (2-3
months) the PSA should be as low as it's going to go...Best wishes and
good health, ron

I think 3 months is more of the norm and it is what my doctor did.

Mine was 3 months.