I'm 33 years old and on doxycycline for acne, about 3 weeks now. can this medication effect my period? taken 2 pregnancy tests negative. help!

No: Taking an antibiotic should not interfere with the regularity of your cycle unless you're using birth control pills.

Doxycycline & menses: Doxycycline does not affect menstrual cycles. If a woman is taking Doxycycline and is on a birth control pill, Doxycycline can potentially make the pill less effective. There are other causes besides pregnancy that could cause a delayed period, such as stress, for example, that can also cause more acne breakouts as well. The best way to make sure about pregnancy is to have a blood test done.