Amenorrhea is a symptom, not a diagnosis — and the causes range from pregnancy to PCOS, thyroid problems and simply not eating enough for what you ask of your body. Here is what each one looks like, and what to do next.
It is one of the first things to go, and one of the last to come back.
Running a menstrual cycle is expensive. It costs energy, and it commits the body to the possibility of pregnancy. When fuel is short — because of how much you are eating, how much you are training, illness or sustained stress — the brain quietly turns the signal down. Nothing is broken. The body is economising.
That is one explanation among several. Polycystic ovary syndrome, an underactive or overactive thyroid, a pituitary issue raising prolactin, premature ovarian insufficiency and some medications all produce the same visible result: no period. They need different care, which is exactly why guessing is the wrong approach and a blood test is the right one.
Understand the common causesBefore any diet change, before any training change.
It is the most common cause of a missed period and the quickest to rule out. Do it even if you are confident it is not that.
Three months without a period is the usual threshold, or six if your cycles were already irregular. If periods have never started by age 15, go now.
When your last period was, what your cycles were like before, and what changed around then — training, eating, stress, illness, weight, medication. Ten minutes of notes makes a ten-minute appointment far more useful.
Free guide
The question most people arrive with, answered in plain English — the common causes, what makes each one more or less likely, and what to have ready for your GP.
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Not a cleaner diet. Not a stricter one. More of it.
This is the part that surprises people, because almost every other health website is pointed the other way. Where a cycle has stopped because of low energy availability, the useful direction is to eat more, eat more regularly, and train less — including the carbohydrate and the fat that get cut first when someone is trying to be good.
In practice that often means a real breakfast rather than a coffee, food around training rather than after it, and three meals that do not depend on willpower. It is rarely about adding a superfood. It is about the total being enough.
Enough food. Enough carbohydrate. Enough rest.
What eating enough looks like
A planned video course covering energy availability, everyday meals, training load and getting more from medical care.
The course is in preparation. The planned price is £47. There is no confirmed launch date and no payments are being taken.
Explore the planned courseTwo resources are in preparation. Both are general education, and neither replaces seeing your GP.
Paid ebook
A written guide covering energy availability, everyday eating, training load and rest, plus how to prepare for a medical appointment.
It is not written yet. The contents and release date have not been confirmed.
Online learning
A planned video learning path working through the same ground in sequence: fuelling a day, adjusting a training week, and getting more from medical care.
The course is not available yet. Its content and launch date have not been confirmed.
Both are in preparation. No orders, enrolments or payments are being taken, and no launch date has been set.
None of these replaces a diagnosis. All of them are worth getting right while you wait for one.
Especially on training days. Something with carbohydrate, protein and fat in it, within an hour or two of waking.
Bread, oats, rice, pasta, potatoes. Carbohydrate availability around exercise is closely tied to the hormonal signalling behind a cycle.
A genuine rest day, not a lighter session. If your training week has no gaps in it, that is a thing to discuss with your clinician.
Worth raising at your appointment, particularly if you eat a restricted diet or your periods were heavy before they stopped.
Plain answers, and an honest line about where a website stops being useful.
Amenorrhea means periods are absent. Primary amenorrhea is when periods have not started by around age 15. Secondary amenorrhea is when periods that were happening stop for three months or more, or for six months if they were already irregular. It is a symptom rather than a diagnosis in itself, which is why finding the cause matters.
There are many possible reasons, and a website cannot tell you which is yours. Pregnancy is the first thing to rule out. Beyond that, common causes include polycystic ovary syndrome, thyroid conditions, raised prolactin from a pituitary issue, premature ovarian insufficiency, some medications and hormonal contraception, and not getting enough energy from food relative to how much you are training or doing. Your GP can narrow it down with a conversation and some blood tests.
It is when the brain reduces the hormonal signals that drive the cycle because the body is not getting enough energy. It is often linked with eating less than you need, training hard, significant stress, or a combination. It can happen at any body weight, including a weight that looks entirely ordinary, which is part of why it gets missed.
Where low energy availability is the cause, eating more and training less is generally the direction clinicians point people in, and for many people cycles do return. It can take months rather than weeks. But it only helps if that is actually the cause, and other causes need different care — which is the reason to get a diagnosis first rather than guessing.
No. Nothing on this site asks you to restrict food, count calories, cut out carbohydrate or lose weight. Where energy availability is involved, restriction makes the situation worse rather than better.
Not yet. A guidebook is planned at £27 and an online video course at £47. Both are in preparation, with no confirmed launch date, and no orders or payments are being taken.
If your periods have stopped for three months, have never started by age 15, or have become irregular in a way that is new for you, make an appointment. Sooner if you also have headaches, changes to your vision, milky discharge from the nipples, hot flushes, or if food or exercise feels difficult to control.
Please do not make that decision from a website. Hormonal contraception affects bleeding patterns, and stopping it has consequences worth discussing. Talk it through with your GP or your contraception clinic.
Absent periods and eating difficulties often travel together, and there is nothing shameful in that. Support is free, confidential and genuinely effective, and you do not need a diagnosis to ask for it.
Pregnancy, PCOS, thyroid and pituitary conditions, premature ovarian insufficiency and low energy availability all stop periods. Here is how they differ and what a GP looks for.
Read articleWhere absent periods are driven by low energy availability, the change that helps is eating more — not less. Here is what that means across an ordinary day.
Read article
How training volume and recovery affect the menstrual cycle, what RED-S means, and how people reduce load without giving up the sport they care about.
Read articleThe hormonal signals that drive a cycle are expensive to produce. When the body is running short of fuel, they are among the first things it turns down.
Low oestrogen over months or years affects bone density. This is the reason clinicians take absent periods seriously in young and active people, and why it is worth raising early.
Carbohydrate availability, particularly around training, is closely tied to the hormonal signalling involved in a regular cycle. Cutting it is rarely helpful here.
Recovery days, sleep and a lighter week are not time off. They change the demand the body is managing, and that demand is part of the picture.
Nutrients worth asking about, especially if your diet is restricted, you are vegetarian or vegan, or your periods were heavy before they stopped.
Significant stress, illness and major life upheaval can all affect the cycle. They belong in the account you give your GP, not just the food and the training.
General information drawn from published guidance including NHS guidance on stopped or missed periods, NHS guidance on PCOS, the NHS Eatwell Guide and the Royal College of Obstetricians and Gynaecologists. This page has not been independently clinically reviewed.
