Nausea occurring during the 1st month of BCP use is a frequent side effect and usually disappears after the first month.

It generally occurs because the patient’s ovarian function has not yet been suppressed, so she has all of her own ovarian hormones, plus the BCP hormones. These high levels of hormone are associated with nausea.

Nausea occurring after the 1st month or severe nausea at any time should make you suspicious of pregnancy, and this is easily ruled out by a negative pregnancy test or convincing patient history.

For those women with persistent nausea and no other cause, this is likely due to the BCPs progestin being insufficient to reliably suppress ovarian function. In this case, every month will be just like the first month, with elevated hormone levels, some from the patient and some from the pill. Switching the BCP to one with a stronger progestin (and a longer half life) will usually resolve this problem. Occasionally, continuous BCPs are needed to continuously suppress ovarian function.

Patients may observe, “I don’t like this pill, it makes me sick all the time. I need something lower dose.” In fact, she needs the opposite. A higher dose progestin to more reliably suppress her own ovarian function. She doesn’t need more estrogen.