First period
What needs checking
2 min read
Most irregularity in the early years needs nothing but time. This is the list that does not.
| Finding | Why it matters |
|---|---|
| No period by 15 | Primary amenorrhea. 98% have started by this age. |
| No period by 14 with excess body or facial hair, or with a history of disordered eating or heavy exercise training | The threshold moves earlier when these are present, because the likely causes differ. |
| No period more than 3 years after breast development began | Measured from thelarche, not from a birthday. |
| No breast development by 13 | Points toward a different set of causes than a delayed period alone. |
| A gap of 90 days or more, even once | Beyond the 95th percentile for cycle length. Not explained by ordinary adolescent irregularity. |
| Cycles shorter than 21 or longer than 45 days once past the first year or two | Outside the adolescent range, not merely the adult one. |
| Bleeding longer than 7 days | Prolonged bleeding at any age. |
| Soaking a pad or tampon every 1 to 2 hours, easy bruising, frequent nosebleeds, or a family history of a bleeding disorder | Screen for a coagulopathy. Heavy bleeding from the very first period is the classic presentation, and it is the finding most often dismissed at this age because there is no personal baseline to compare against. |
The First Periods Checker works through this list and the cycle parameters in the first two years, and sorts the answer into one of four levels of urgency.
Criteria per ACOG Committee Opinion No. 651, Obstet Gynecol. 2015;126(6):e143–e146. Evaluation for precocious puberty follows a separate pathway; thresholds for that assessment are not covered on this page.
Seek care the same day for:
- soaking through a pad or tampon every hour for two hours in a row;
- feeling faint, dizzy or breathless, or a racing heart, with bleeding;
- severe pelvic pain of sudden onset;
- cyclic pelvic pain with no bleeding ever having occurred — this can indicate an obstruction of the reproductive tract.