Oral contraceptives: how they work and what to expect
Oral contraceptives prevent pregnancy through hormones. Here's how they work, who they suit, and what side effects to watch for.
How oral contraceptives work
Oral contraceptives, or birth control pills, use synthetic hormones to prevent pregnancy. They work in three ways: by stopping ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining.
Types of oral contraceptives
Combined oral contraceptives contain both estrogen and progestin. Progestin-only pills (the mini-pill) contain only progestin and suit people who cannot take estrogen.
Effectiveness
Oral contraceptives are over 99% effective when taken perfectly every day at the same time. Typical use effectiveness is around 91% because missed pills and drug interactions reduce protection.
Common side effects
Many people experience mild side effects in the first few months: nausea, breast tenderness, headaches, or mood changes. Most settle within 2-3 months. Serious side effects are rare but include blood clots, stroke, and heart attack, especially in people who smoke or have certain medical conditions.
Who should avoid them
Oral contraceptives are not suitable for people with a history of blood clots, stroke, or heart attack. People over 35 who smoke should use an alternative. Certain medications and health conditions affect how well they work.
Getting started
You need a prescription from a healthcare provider. Telehealth options make this simpler: you can consult a clinician online, describe your medical history, and receive a prescription without leaving home.