Can having diarrhea make the pill less effective?

Having “loose” poop every now and then probably won’t affect how well your pill works, but severe diarrhea (e.g. if you have it several times for more than 48 hours) might because the hormones in the pill are absorbed through your intestines over time. So, if you rely on the pill for pregnancy prevention and you have severe diarrhea that lasts more than 48 hours, it’s a good idea to use a backup method like condoms if you have sex while you’re sick and for the 7 days after you recover.