Do you ever take old antibiotics?

Question

My bf and I had sex today, and I wiped myself beforehand and peed afterwards (altho not a lot of pee came out, only a little), and then I got up to pee again a little later. I don’t think UTIs can develop in less than 12 hours but I was scared, so I took a leftover antibiotic from the last time I had a UTI (which was 2 months ago). 
I know you’re supposed to take all your meds in one round, but I forgot one last time. It’s not like I was saving it for this moment. 
I know you’re also not supposed to take left over meds (in case you need a diff. one) but I get the same prescription any time this happens, and I feel like this pill might’ve knocked out any tiny chance of me having a UTI. It gave me hope.
Is this bad?
Also does planned parent hood prescribe antibiotics for less than the emergency room does?

Answer

You should never have old antibiotics in the first place. It’s really dangerous to not finish a round of antibiotics even if you think the issue is gone.  It’s a real fear in the science and medical fields right now that diseases will become stronger than our medicine because when people don’t finish antibiotics, the bacteria doesn’t completely die and then just becomes stronger before it moves on.   Seriously, in the future, finish your antibiotics... most people don’t realize that it truly affects our future in medicine.  
So no, don’t take just a few old ones until you feel better.  Go get some new ones and complete the whole prescription.

Answer

Taking one capsule will not change anything but for future reference it's never safe to take old antibiotics