Is a pregnancy test 100 percent accurate 21 days after unprotected intercourse?

99% accurate: Pregnancy tests are reported to be about 99% accurate when done correctly. False positives & false negatives can occur. For the most accurate results with a urine test take the test after the first day of your missed period. If such timing is hard a blood test may be preferable. Repeat the test if there are uncertainties. I wish you well with your health!

Test: At 21 days the test would be 100 percent for the unprotected episode. Now remember, if you have been sexually active protected sex is not 100 percent preventative of pregnancy. False negatives with pregnancy tests are usually associated with taking the test too early. Within a week or so.

Pregnancy test : To answer this most accurately, there are very rare circumstances where a pregnancy test is positive and the person is not actually pregnant but has a tumor producing a hormone. I want to emphasize this is very rare, and most of the time a positive pregnancy test at 21 days is consistent with being pregnant.

See below: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.