Birth control pills cause a range of side effects, from mild and temporary symptoms like nausea and spotting to rare but serious risks like blood clots. Most common side effects resolve within two to three months as your body adjusts to the hormones. Here’s what to expect and what actually matters.
Common Side Effects in the First Few Months
When you first start the pill, your body needs time to adjust to the new hormone levels. The most frequently reported side effects during this window include nausea, breast tenderness, headaches, spotting between periods, and bloating. About 10% of women experience new headaches after starting a combined pill. These early side effects typically fade within two to three months.
Spotting, or breakthrough bleeding, is one of the most common reasons people consider stopping the pill early. It happens because the uterine lining is adjusting to a thinner state under hormonal influence. If you’re still spotting after three months, switching to a different formulation often resolves it. Missing pills or taking them at inconsistent times makes spotting more likely.
Combined Pills vs. Progestin-Only Pills
Combined pills contain both estrogen and a progestin, while progestin-only pills (sometimes called the minipill) skip the estrogen entirely. The side effect profiles overlap but differ in important ways.
Progestin-only pills are more likely to cause irregular bleeding and spotting than combined pills. Some people on the minipill have lighter periods, while others stop getting periods altogether. The minipill does not carry the same blood clot risk as combined pills, which is why it’s often recommended for people who smoke, are over 35, or have a history of migraines with aura.
Combined pills, because of their estrogen component, are more commonly linked to nausea, breast tenderness, and the cardiovascular risks discussed below. They do, however, tend to produce more predictable monthly bleeding patterns.
Mood Changes and Depression
Mood-related side effects are among the most debated in contraceptive research. Many people report increased irritability, mood swings, or low mood after starting the pill, and these reports go back decades. But the clinical evidence is genuinely mixed.
Several large studies have found higher rates of clinical depression among pill users compared to non-users, based on markers like antidepressant prescriptions and documented diagnoses. Other equally large studies found no difference at all, and a few even suggested hormonal contraception could have a protective effect on mood. One consistent finding is that adolescents and people who start the pill during their teenage years may be more vulnerable to negative mood effects than adults who start later.
Interestingly, some women who experience severe premenstrual mood symptoms actually find their mood stabilizes on the pill, because the hormonal fluctuations that trigger those symptoms are dampened. If you notice a persistent shift in your mood after starting the pill, it’s worth taking seriously, but it’s also worth knowing that not everyone experiences this and switching formulations can help.
Weight Gain: What the Evidence Shows
Weight gain is one of the most commonly cited concerns about birth control pills, but clinical evidence doesn’t support it. A Cochrane review, which is considered the gold standard for evaluating medical evidence, looked at trials comparing combination pills and patches against placebos. The four trials with a placebo or no-treatment group found no evidence that combination contraceptives cause weight gain.
That said, some people do notice a few pounds of water retention in the first months, which is hormonally driven and usually temporary. This is different from actual fat gain. If you’re experiencing significant, sustained weight changes on the pill, other factors are likely contributing.
Blood Pressure Effects
Combined birth control pills can raise blood pressure slightly. Cross-sectional studies from multiple countries found that pill users had systolic blood pressure (the top number) about 2.6 to 5.8 points higher than non-users, with the bottom number rising by 1.8 to 3.6 points. For most people, this is a small, clinically insignificant change.
However, some individuals are more sensitive. Prospective studies have estimated that anywhere from 4% to 18% of combined pill users develop elevated blood pressure, with some studies showing increases as high as 7 to 17 points in systolic pressure. This is why blood pressure checks are a standard part of pill prescriptions. If your readings start climbing, a progestin-only method or a non-hormonal option is typically a better fit.
Blood Clot Risk
The most talked-about serious risk of combined birth control pills is venous thromboembolism, or blood clots forming in the veins. The estrogen in combined pills increases clotting factors in the blood. To put the risk in perspective: among women not using hormonal contraception, roughly 1 to 5 out of every 10,000 will develop a clot in a given year. Among combined pill users, that number rises to 3 to 15 per 10,000.
The type of progestin in your pill matters. Pills containing older progestins like levonorgestrel carry a lower clot risk, around 8 per 10,000 women per year. Newer formulations containing drospirenone are associated with a higher rate, estimated at 10 to 15 per 10,000. For context, pregnancy itself carries a significantly higher clot risk than any birth control pill.
Certain factors multiply this risk substantially: smoking (especially over age 35), obesity, a personal or family history of blood clots, and prolonged immobility like long flights or recovery from surgery. If you have any of these risk factors, a progestin-only or non-hormonal method is generally a safer choice.
Effects on Cancer Risk
Birth control pills have a complex relationship with cancer, reducing the risk of some types while slightly increasing the risk of others.
On the protective side, women who have ever used oral contraceptives have a 30% to 50% lower risk of ovarian cancer and at least a 30% lower risk of endometrial cancer compared to women who never used them. These protective effects increase with longer use and persist for years after stopping the pill.
On the other side, a large analysis of more than 150,000 women found that those who had ever used oral contraceptives had a 7% overall increase in breast cancer risk. Current users face a roughly 20% to 24% increase, though this elevated risk does not grow with longer use and gradually fades after stopping. In absolute terms, for younger women whose baseline breast cancer risk is already low, this translates to a very small number of additional cases.
Warning Signs That Need Immediate Attention
While serious complications are rare, certain symptoms while on the pill require urgent medical evaluation. These include sudden severe abdominal pain, chest pain or shortness of breath, severe headaches that feel different from your usual headaches, vision changes like blurriness or flashing lights, and severe leg pain or swelling in one calf. These can signal a blood clot, stroke, or other vascular event. They are uncommon, but recognizing them matters because early treatment makes a significant difference in outcomes.
How Long Side Effects Last
Most nuisance side effects, including nausea, breast tenderness, spotting, headaches, and bloating, resolve within the first two to three months on the pill. If side effects persist beyond that window, switching to a pill with a different type or dose of progestin, or a different estrogen dose, often helps. There are dozens of formulations available, and what causes side effects in one person may work perfectly for another. If you’ve tried multiple pills and still have problems, non-pill options like IUDs, implants, or the ring deliver hormones differently and may sidestep the issues you’re experiencing.