I'm not aware of any bad side effects...

You can read the back of the box to see any possible side effects. I went to their website but didn't see anything about side effects. There was an area where you could send them an email/ ask a question. There was a warning to ask your doctor before taking it if you are pregnant, breastfeeding or on the pill.

I think I may be getting a yeast infection and to prevent it I wanted to take the homeopathic azo yeast pills but Im also on birth control. Will it effect my birth control in any way?

Here is what it says at the website:
Can I take AZO YEAST® with oral contraceptives (birth control pills)?
Please review the ingredient listing with your healthcare professional before taking AZO YEAST® with your current medications.

um, i experienced lotsa gas and diarrhea. not sure whether the yeast infection or the side effects were worse. i will try taking azo yeast again though, because it actually seemed to be working (diflucan, monostat aren't helping) and i have a chronic situation i need to be able to treat myself. sigh.