Painful periods only on day 1 — is it normal?

Cramping on day one is normal. The uterus contracts to shed its lining, driven by prostaglandins, and mild to moderate pain for a day is called primary dysmenorrhoea. Anti-inflammatories such as ibuprofen work well for it, and they work considerably better if started at the first sign of pain rather than once it has peaked. What is not normal, and is too often dismissed: pain severe enough to keep you off work or school, pain that is getting worse over time, pain lasting beyond the first day or two, pain during sex or when opening your bowels, or heavy bleeding alongside it. Those point toward endometriosis or adenomyosis. This matters because the average delay between symptoms starting and endometriosis being diagnosed is measured in years, largely because severe period pain gets normalised — by families, sometimes by doctors, and often by women themselves. If your pain is affecting your life, that is sufficient reason to be assessed. You should not have to justify it, and you should not have to wait until it is unbearable.