Do expired birth control pills still work properly?

Yes and No. Each brand of Birth Control is different. Your period may or may not be longer than length of the inactive pills (the 4-7 pills at the end of the pack that are a different color). The only pills that "ok" to skip or miss are the ones that are inactive. Some pill brands such as Loesterin 24 are not just placebos (sugar pills) but they contain iron which is helpful when you are on your period because it helps replace the nutrients in the blood lost during your menstrual period. There is a reason the inactive pills are there. They are there to help you remember when to take the next active pill. It is okay if you miss an inactive pill while on your period but I would recommend taking them anyways just to ensure that you know exactly which day to start taking your active pills again or to gain nutrients that are lost during your period.