I get side effects even from 1.25mg 2 times a week.
It still inhibits 5-alpha-reductase and lowers your DHT, so it's working.
After taking 1 pill of finasteride, the drug itself is largely eliminated from the body in 1-2 days given that the half life of finasteride is about 4-6 hours (after five half lives a drug is significantly reduced in the body). However the same is not true of DHT levels. After a single dose of finasteride, DHT levels are reduced by 60 % (ie from 65 ng/dL to 25 ng/dL). However, the DHT levels don't rise back up quickly even though the drug is out of the body. Rather, DHT levels rise slowly increasingly just 15-20 % after the second day (ie from 25-30 ng/dL up to 30-35 ng/dL).