 [ Symptoms ] is it safe to use weight loss product alli while taking synthroid medicine [ Disease ] hi ok it works like this the bc pill 99 perfect in you not getting pregnant the bugger is that 1 its that 1 that can get you and its not down to the length of time you have been on it so as you have not had a good period then either do an hpt or get a test done at your doctors its the only way to find out good luck