Can i take a prgrant test after 16 days of my period?

Not clear: I am not sure if you mean 16 days after period ended/started or that your period has lasted 16 days. Regardless, most home pregnancy tests are accurate within two weeks after conception, so it really depends on if you had unprotected sex and when you had sex since you last normal period, as to whether performing a urine pregnancy test would be appropriate or accurate.