Progestin-only pills are birth control pills that contain progestin but do not contain estrogen. They are often called the mini-pill and may be preferred by people who cannot take estrogen, are breastfeeding, or want an estrogen-free option. They can be effective when taken correctly, but some versions need to be taken at the same time every day to work well. Common reasons people notice differences include irregular bleeding, spotting, missed periods, mood changes, acne, breast tenderness, or convenience. Different versions may vary by progestin type, timing flexibility, bleeding pattern, cost, and side effects.