What normal actually looks like
In the first year or two after periods start, cycles are commonly unpredictable, and that on its own is not a worry. Once things settle, most cycles fall between 21 and 35 days, and varying by a few days each month is ordinary.
A useful way to think about it: irregular and settling is normal, irregular and getting worse is information.
| Pattern | What it usually means |
|---|---|
| Unpredictable in the first 1 to 2 years | Usually normal, keep a simple record |
| 21 to 35 days, varies by a few days | Normal once established |
| Cycles becoming longer and gappier over a season | Check fuelling and load, then see a GP |
| No period for 3 months or more | GP appointment |
| Very heavy or very painful with irregularity | GP appointment |
Sorting normal from worth-checking
The training and growth link
When cycles drift out during a season of higher training, a growth spurt, exam stress or weight loss, the most common explanation in young athletes is that the body is short of energy. It is not a sign of being fitter.
This is the version most parents miss, because performance can look fine for a while before anything else gives way.
Track it before you worry about it
- Note the first day of each period, nothing more complicated than that.
- Add a word on symptoms, energy and how training felt.
- Do it for three months, then look at the pattern rather than a single month.
- Take that record to the GP appointment, it saves a lot of guesswork.
Practical checks to make first
- Is she eating before and after training, on every training day?
- Has training gone up recently without food going up too?
- Is she growing quickly at the moment?
- Is she getting eight to ten hours of sleep most nights?
- Have there been repeated niggles, or any bone injury?
When to book the appointment
See a GP if there has been no period for three months, if periods have not started by 15, if bleeding is heavy enough to cause tiredness or affect school, if pain stops normal activity, or if irregularity comes alongside repeated injuries or persistent fatigue.
Ask specifically about energy availability, bone health and iron levels. Those three questions turn a general appointment into a useful one for an athlete.