I have been on Synthroid for 5 years. I started a low dose of birthcontrol about 3 months ago to help regulate my periods. When it came to the end of my first month on the pill my period started on the first day of the sugar pill. The second month was the same, right on time. On the third month it did the same too. The only thing different is I only spotted and I mean barely spotted. Shortly after that I noticed I started feeling real tired. I could feel my thyroid acting up. It was hard to say what was causing all of this. So I was curious to know can thyroid meds interfere with a low dose of b/c pills? I take my thyroid meds in the morning and b/c at night.