Much of this site is about energy, food and training, because that cause is common and frequently missed. But it would be a poor site if it left you thinking that is the only possibility.
Several medical conditions stop periods and have nothing to do with how much you eat or exercise. Each needs its own diagnosis and its own treatment, and no amount of eating differently will address them.
Polycystic ovary syndrome
PCOS is one of the most common endocrine conditions affecting people of reproductive age. Periods may be irregular, infrequent or absent.
It may be accompanied by acne, unwanted hair growth on the face or body, thinning hair on the scalp, or difficulty managing weight — but many people with PCOS have none of these, and having one of them does not mean you have PCOS.
Diagnosis uses a combination of symptoms, blood tests and sometimes an ultrasound. Management depends on which features affect you most and may involve several different approaches. The NHS page on PCOS is a reasonable starting point.
Thyroid conditions
The thyroid influences a great deal, the menstrual cycle included. Both an underactive thyroid (hypothyroidism) and an overactive one (hyperthyroidism) can disturb or stop periods.
Other signs might include tiredness, weight change, feeling unusually cold or hot, changes to hair and skin, or palpitations. Thyroid function is simple to test and very treatable, which is why it is almost always on the first round of blood tests.
Raised prolactin
Prolactin is the hormone behind milk production. When it is raised outside pregnancy and breastfeeding, periods can stop.
Causes include a small benign growth on the pituitary gland called a prolactinoma, certain medications, and an underactive thyroid. Additional signs worth reporting promptly are milky discharge from the nipples, persistent headaches and changes to your vision.
Premature ovarian insufficiency
Sometimes the ovaries stop functioning as expected before the age of 40. Alongside absent or irregular periods there may be hot flushes, night sweats, difficulty sleeping or vaginal dryness.
POI needs proper diagnosis and ongoing care, including attention to bone and cardiovascular health, and it has implications for fertility that deserve a proper conversation rather than a web page.
Medication, including contraception
Several hormonal contraceptives reduce or stop bleeding, and that is usually expected rather than a concern. Some other medications also affect the cycle.
Never stop or change prescribed medication to test a theory. Raise it at your appointment instead.
Structural and other causes
Less commonly, periods are absent for structural reasons, including scarring inside the uterus after surgery or infection, or differences present from birth that typically come to light when periods never start at all.
The common thread
All of these are distinguished by the same unglamorous process: a conversation, some blood tests, sometimes a scan. That is why this site keeps returning to the same recommendation. Understanding the possibilities is useful. Acting on a guess is not.
General education, not a diagnosis. If your periods have stopped, your GP is the next step.
Explore the guides