Birth control effectiveness timing depends on the type:

• Combination birth control pills work immediately if started within the first 5 days of the menstrual cycle; otherwise, they take 7 days to become effective.
• Progestin-only pills (mini-pills) start working immediately if taken in the first 5 days of the cycle but take 2 days if started later.
• Birth control patches, rings, and shots follow similar timing: immediate if started within 5 days of period onset, otherwise 7 days to work.
• Barrier methods like condoms and spermicides work immediately when used correctly.
• Vasectomy and tubal ligation take longer to become effective, with vasectomy requiring several months for sperm clearance.

It is recommended to use a backup method for the first 7 days if birth control is not started at the beginning of a period. This ensures protection against pregnancy during the waiting period.