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Medically reviewed guide · Last updated: 1 August 2026 · Reading time: approx. 9 min
Missed Period: Pregnancy, PCOS or Medication?
At a glance
The first step is always a pregnancy test— even with reliable contraception, even when it seems unlikely. No method of contraception is a hundred per cent safe, and every further thought changes with that one result.
A single missed cycle is not a finding in itself.It needs looking into when the bleeding stays away for three months in a row, or six months if your cycle is irregular anyway.
The most common causes apart from pregnancyare hormonal: PCOS, a thyroid disorder in either direction, a raised prolactin level, and a lack of available energy through stress, being underweight or intensive sport.
Medicines are an underestimated trigger.Antipsychotics in particular can stop the cycle completely by raising prolactin — that is well known, well studied and treatable.
Your period is a vital sign.If it stays away for longer without a pregnancy, oestrogen is usually missing — and that affects more than your cycle, it affects your bone density too.
Seek urgent medical advice ifyour period stops and milk leaks from your breast outside breastfeeding, if there are visual disturbances or newly appeared headaches, if there is marked unintended weight loss, or if your periods stop for good before the age of 40.
The most common causes compared
Cause
Typical pattern
Typical accompanying signs
First step
Pregnancy
The period stops after a previously regular cycle
Tenderness in the breasts, nausea, tiredness
Pregnancy test, whatever your contraception
PCOS
Irregular for years, long gaps, then bleeding
Acne, increased body hair, hair loss, weight gain
Gynaecological assessment with hormone levels and ultrasound
Thyroid (under- or overactive)
The cycle becomes lighter, less frequent, or stops altogether
Feeling cold and tired, or the opposite: restlessness and a racing heart
TSH measured in the laboratory
Hypothalamic amenorrhoea (lack of available energy)
The cycle stops after a stressful phase, weight loss or a build-up in training
It comes first not out of politeness, but because it determines everything that follows. Pregnancy is by far the most common reason for a previously regular period to stop — and it can happen even with careful contraception. No contraceptive is a hundred per cent safe, and vomiting, diarrhoea, missed doses or certain other medicines can weaken hormonal contraception further.
In practice that means: a test from a pharmacy or a chemist, at the earliest on the day your bleeding is due, ideally with your first urine of the morning. If it is negative and your period still does not come, repeat it after about a week before you start looking in other directions. If it is positive, the next step is a gynaecology practice.
What to bear in mind with hormonal contraception. On the pill, an implant or a hormonal coil, bleeding can become lighter or stop altogether — with some products that is a known and harmless effect. What can affect how well you are protected is set out in the guide Medications and contraception.
The causes in detail
PCOS: the most common hormonal cause
With PCOS, ovulation often does not happen. The second half of the cycle is then missing, the bleeding is pushed further back or stays away entirely. What is typical is a pattern that has been there since adolescence: very long cycles, unpredictable bleeding, often together with acne, increased body hair, hair loss at the crown and weight gain.
The time factor matters: if bleeding stays away for a long time, the lining of the womb builds up unchecked. That is why with PCOS care is taken to make sure that bleeding happens at certain intervals — which route is suitable for that is decided by the practice treating you.
The thyroid — in both directions
The thyroid helps steer the cycle indirectly, and it does so in both directions. An underactive thyroid can suppress ovulation by raising prolactin; typical companions are feeling cold, fatigue and weight gain. An overactive thyroid tends to lead to light, infrequent or absent bleeding, often with inner restlessness, a racing heart and weight loss. TSH gives the first orientation here — both disorders respond well to treatment.
Hypothalamic amenorrhoea: when energy is missing
The cycle is not a fixed institution but a function that the body shuts down when it has to. The control centre in the brain — the hypothalamus — reacts sensitively to sustained stress, too little available energy and high physical demands. If the energy balance is negative for longer, it turns the steering hormones down: ovulation does not happen, and neither does the bleeding.
This does not only affect people who are markedly underweight. A moderate weight loss, a very strict way of eating, an intensive build-up in training or a demanding phase of life without recovery can be enough — especially in combination. Feeling cold, low blood pressure, exhaustion, sleep problems and waning sexual interest often come with it.
This is not a question of discipline or fault, but a sensible response to a situation of scarcity — and it is reversible: when available energy rises again, the cycle comes back for many people. Until then, though, the low oestrogen level remains an issue that goes beyond the cycle.
Raised prolactin
During breastfeeding, prolactin stimulates milk production and at the same time suppresses ovulation. If it is raised outside pregnancy and breastfeeding, the same thing happens: the cycle becomes irregular and finally stops. The most striking clue is milk leaking from the breast outside breastfeeding — sometimes only a few drops when pressure is applied. Causes include medicines, an underactive thyroid and benign enlargements of the pituitary gland. If headaches or visual disturbances come with it, that needs assessing promptly.
Premature menopause before the age of 40
If the ovaries stop working before your 40th birthday, this is called premature ovarian insufficiency. The pattern resembles that of the menopause, only considerably earlier: first irregular cycles, then longer gaps, together with hot flushes, night sweats and sleep problems. The diagnosis needs repeated laboratory results — important not least because the early lack of oestrogen has long-term consequences for bones and blood vessels and is usually treated.
After coming off the pill
After stopping the pill, your own cycle needs time. On the pill the body's own control system rests, and it does not start up again immediately for everyone: for many the first period of their own comes within a few weeks, for some it takes months. This phase is often called “post-pill amenorrhoea”.
A point that takes the pressure off: the pill does not usually cause a lasting cycle disorder. If the bleeding stays away for a longer time, what generally resurfaces is a pattern that was already there before and had been masked by the pill — frequently PCOS. Rule of thumb: after about three months without bleeding it is worth getting it looked into rather than waiting any longer.
The medication angle: the underestimated cause
If your cycle stopped close in time to starting a medicine or increasing its dose, that is not a coincidence but the first thing to suspect. These groups are known for it:
Antipsychotics: the classic trigger
Many antipsychotics block dopamine — precisely the messenger substance that puts the brakes on prolactin release. If the brake comes off, prolactin rises, ovulation does not happen and the cycle stops; sometimes milk leaking from the breast comes with it. How strongly a product raises prolactin differs markedly: risperidone is one of the active ingredients with a pronounced effect, whereas quetiapine usually influences it less.
Do not stop it on your own — but do raise it A cycle that has stopped is a good reason to raise the subject at the practice treating you — but not a reason to reduce an antipsychotic on your own: that can trigger a relapse of the underlying condition. Often the prolactin level can be measured and the treatment adjusted together. How to prepare for a conversation like that is set out under Preparing for your doctor's visit.
Other medicines and treatments
Chemotherapy — many substances damage the reserve of egg cells. The cycle can pause and then return, or stop for good; preserving fertility should be discussed before treatment starts wherever possible.
Glucocorticoids — longer treatment with prednisolone at a higher dose can interfere with the hormone axis.
Opioids — painkillers such as tramadol can dampen the steering hormones when used over a longer period.
Antidepressants — considerably less often: individual active ingredients such as sertraline can raise prolactin slightly. Usually the cycle is unremarkable on this group.
Stomach medicines and medicines for nausea — individual active ingredients also raise prolactin.
In practice that means: take a complete list to your appointment — prescription medicines, over-the-counter products and food supplements. The link between the start of a treatment and the end of your cycle only becomes noticeable once both are laid out side by side.
Why this is more than a missing bleed
Your period is a vital sign. It shows that the hormone axis is working — and oestrogen acts not only on the womb, but also on bones, blood vessels, mucous membranes and mood.
If the bleeding stays away for months without a pregnancy, a low oestrogen level is usually behind it. The most important silent effect concerns the bones: oestrogen slows down bone breakdown. If it is missing for a long time, bone density falls — with particular consequences in younger women, because these are the years in which bone mass should still be being built up. That raises the risk of osteoporosis later in life.
A period that has been absent for months is therefore not something to sit out just because you are not trying to conceive right now. That very thought — “it does not bother me” — costs bone density that is hard to win back later.
What else makes sense If the bleeding stays away for a longer time, the supply of vitamin D and calcium is often looked at as well and, depending on the situation, a bone density scan is considered. That does not replace treating the cause, but it is part of looking after yourself.
Self-tests: first clues at home
These observations do not replace a diagnosis. But they will help you lay the right trail before you go to the practice.
The test first: a pregnancy test with your first urine of the morning, repeated after a week if your period still does not come.
The timeline: when was your last bleed? What changed in the three months before that — a new medicine, weight loss, a new training load, the pill stopped, a demanding phase of life?
The breast check: does fluid come out of the nipple when you press, even though you are not breastfeeding? A concrete clue to raised prolactin.
The thyroid view: are you noticeably cold, tired, and have you put on weight? Or the other way round: a racing heart, restlessness, sweating? Both lead to the same first laboratory value.
The energy check: are you eating enough for your activity level? Are you cold all the time, sleeping badly, is your libido gone? That points to a shortage of available energy.
The back story: was your cycle already irregular before the pill? That question often decides whether this is an after-effect of stopping it or a pattern that has been there for longer.
Warning signs: when not to wait
Milk leaking from the breast outside breastfeeding
Newly appeared headaches or visual disturbances, especially gaps in your field of vision
A missed period together with marked, unintended weight loss
Bleeding that stops for good before the age of 40
No first period by the age of 15
The cycle stops after starting a new medicine
This combination needs examining promptly Milk leaking outside breastfeeding together with headaches or visual disturbances can point to an enlargement of the pituitary gland pressing on the crossing of the optic nerves. That is usually benign and treatable, but it should not be left to wait. If you have sudden, extremely severe headaches with visual disturbances, call 112 (emergency services in Germany).
The treatment pathway: what happens at the practice
The work-up for a missed period is well standardised. If you know what is coming, the appointment becomes easier to plan.
Rule out pregnancy. Even if you have already tested yourself, this is usually confirmed.
Conversation and timeline. Cycle length then and now, how your weight has changed, sport, stress, medicines, previous conditions, family history. Most of the direction is decided here.
Examination and ultrasound. The lining of the womb and the ovaries are assessed — among other things how far the lining has built up and whether the picture typical of PCOS is present.
Hormone levels in the laboratory. TSH, prolactin, FSH, LH and oestradiol are among the usual ones; the selection follows the suspicion, and the timing of the blood test is specified for you. How to read results like these is explained in the guide understanding blood values.
Targeted additional tests. Depending on the result, follow-up checks, a progestogen challenge test, imaging of the head if prolactin is markedly raised, or a bone density scan may be added.
Treating the cause. Settling the thyroid, lowering prolactin, adjusting medication, improving the energy balance, making sure bleeding happens regularly in PCOS. Which route fits depends a great deal on whether you want to conceive — the decision is always taken by the practice treating you, together with you.
The timeline that shortens your appointment
Cycles, medication start dates and symptoms side by side — visible instead of remembered.
A cycle cannot be forced, and where the cause is structural no lifestyle change will help. What you can influence is the energy and stress side — and how quickly a cause is found.
Eat enough for your own workload — if you increase your training volume, your intake has to follow. The cycle is often the first system to be switched off when there is a gap.
Build recovery into the plan — sleep and training-free days are not slacking, they are part of hormone regulation.
Write your cycle down, even when it is irregular — “nothing since the spring” is a finding, “somehow rarely” is not.
Date the start of every medicine — without the date, the link to your cycle stays invisible.
Get it looked into after three months — the most common avoidable delay is waiting. Three months without bleeding is reason enough for an appointment.
Your medication list, ready for the appointment
Every active ingredient with its start date — so the link to your cycle stands out.
As a rule of thumb: three months without bleeding if your cycle was regular before, or about six months if your cycle is irregular anyway. Sooner if milk leaks outside breastfeeding, if there are visual disturbances or marked weight loss as well, or if the cycle stopped after a new medicine. A pregnancy test comes first in every case.
For many people the first period of their own comes within a few weeks, for some it takes a few months. The pill does not usually cause a lasting cycle disorder. If the bleeding stays away for longer than about three months, a pattern that was already there before often comes back to the surface — that should be looked into rather than waited out.
Yes, this is known as hypothalamic amenorrhoea. Sustained stress, too little available energy and high physical demands act on the control centre in the brain, which then turns the cycle hormones down. Usually it is a combination of these factors at work. For many people the cycle returns once energy intake and recovery are sufficient again.
The best known are antipsychotics, which raise prolactin by blocking dopamine and so suppress ovulation. Chemotherapy, longer treatment with steroids at a higher dose, opioids and certain stomach and anti-sickness medicines also come into question; antidepressants are rarer. Never stop anything on your own — take your complete medication list to the appointment instead.
Because bleeding that has been absent for months without a pregnancy usually indicates a low oestrogen level. Oestrogen slows down bone breakdown. If it is missing over a longer period, bone density falls and the risk of osteoporosis later in life rises. That is why a missed period is a reason to get it looked into even if you are not trying to conceive.
It is a clue to a raised prolactin level, which at the same time suppresses ovulation and can stop the cycle. Causes include medicines, an underactive thyroid or a usually benign enlargement of the pituitary gland. The prolactin level is easy to measure in the blood. If headaches or visual disturbances come with it, see a doctor promptly.
Gesundheitsinformation.de (IQWiG): Cycle disorders and absent periods — German source. Accessed 2026.
gesund.bund.de (German national health portal): The menstrual cycle, PCOS and thyroid conditions — German source. Accessed 2026.
MSD Manual, Consumer Version: Amenorrhoea and galactorrhoea. Accessed 2026.
German S2k guideline on the diagnosis and treatment of polycystic ovary syndrome (led by the DGGG, AWMF register) — German source. Accessed 2026.
German S3 guideline on the peri- and postmenopause: diagnosis and interventions (led by the DGGG, AWMF register) — German source. Accessed 2026.
Summaries of product characteristics for the active ingredients mentioned (quetiapine, prednisolone, tramadol, sertraline). Accessed 2026.
This article is for general information and does not replace medical advice, diagnosis or treatment. The self-observations described are a guide for preparing the conversation with your doctor and not a diagnosis. If milk leaks from your breast outside breastfeeding, if you have newly appeared headaches or visual disturbances, if you have marked unintended weight loss, or if your bleeding stops for good before the age of 40, please contact a doctor; if you have sudden, extremely severe headaches with visual disturbances, contact the emergency services.
