Menstruation and Epilepsy
Can the menstrual cycle affect seizures?
For some people with epilepsy, seizures appear to change at particular points in the menstrual cycle.
One person may notice more seizures shortly before or during a period. Another may notice changes around ovulation. Many people notice no consistent relationship at all.
The connection between menstruation and epilepsy is real, but it is not as simple as saying that periods cause seizures.
Hormonal changes across the menstrual cycle can influence activity in the brain, while epilepsy and some antiseizure medicines can also affect menstrual and reproductive health.
Understanding whether there is a genuine pattern usually requires looking at seizures and menstrual cycles over time.
The menstrual cycle is more than the days of bleeding
The menstrual cycle begins on the first day of menstrual bleeding and continues until the day before the next period begins.
During that cycle, levels of reproductive hormones change.
Two hormones commonly discussed in epilepsy research are:
Oestrogen
Oestrogen has complex effects on the brain.
Experimental research suggests that, under some circumstances, oestrogen can increase neuronal excitability. However, its effects vary according to the type of oestrogen, concentration, brain region and other biological factors.
It should therefore not simply be described as a hormone that "causes seizures".
Progesterone
Progesterone and some of the substances produced when the body breaks it down can enhance inhibitory signalling in the brain, including through GABA-related mechanisms.
Falling progesterone levels at certain stages of the menstrual cycle are one proposed explanation for why some people experience increased seizure susceptibility at those times.
The relationship between reproductive hormones and epilepsy is considerably more complicated than a simple balance of "bad oestrogen" and "good progesterone".
What is catamenial epilepsy?
Catamenial epilepsy describes a recurring pattern in which seizures become more frequent at particular stages of the menstrual cycle.
It is not a separate epilepsy syndrome.
A person may already have focal epilepsy, generalised epilepsy or another form of epilepsy and also experience a catamenial pattern.
Research has commonly described three patterns:
C1 — Perimenstrual pattern
Seizures increase around the beginning of menstruation.
This is the pattern most commonly associated with the fall in progesterone that occurs before a period.
C2 — Periovulatory pattern
Seizures increase around ovulation, generally around the middle portion of the cycle.
Changes in oestrogen around ovulation have been proposed as one possible mechanism.
C3 — Luteal or inadequate-luteal-phase pattern
This pattern is associated with cycles in which progesterone production after ovulation is lower or the normal hormonal pattern is disrupted.
Catamenial patterns can occur in people with focal or generalised epilepsies.
Related Information Hub page:
Catamenial Epilepsy — coming later
How common is catamenial epilepsy?
Figures vary considerably between studies because researchers have not always used the same definition or method of measuring it.
Some reviews have estimated that around four in ten women with epilepsy may show some degree of catamenial seizure exacerbation.
That figure should not be interpreted as meaning that four in ten women have seizures caused by menstruation.
It means that menstrual-cycle-related seizure patterns have been identified in a substantial proportion of women studied.
Importantly, a 2026 review published in Epilepsia highlighted significant inconsistencies in how catamenial epilepsy has been defined and measured across research studies. It also noted that seizure activity can follow longer biological rhythms that are not necessarily caused by menstruation.
So an apparent monthly pattern needs careful interpretation rather than assumption.
One bad period does not establish a pattern
Having several seizures during one menstrual period does not necessarily mean someone has catamenial epilepsy.
Seizures fluctuate for many reasons.
For example, around the same time someone is menstruating they might also experience:
disturbed sleep
pain
stress
illness
missed medication
changes in appetite
dehydration
emotional changes
or other individual seizure triggers.
The important feature of suspected catamenial epilepsy is a repeated relationship between seizure activity and particular parts of the menstrual cycle.
Keeping a seizure and menstrual diary
One of the most useful things someone can do if they suspect a menstrual pattern is to record both cycles together.
A diary might include:
the first and last day of menstrual bleeding
seizure dates
seizure times
seizure type
seizure duration
seizure clusters
possible auras or warnings
recovery afterwards
missed or late medication
sleep
illness
stress
alcohol where relevant
unusual bleeding
and any other suspected triggers.
Epilepsy Action recommends keeping seizure and menstrual information for around three months when investigating a possible catamenial pattern.
Longer records may sometimes give an even clearer picture, particularly when menstrual cycles or seizures are irregular.
Why three months may not always be enough
Three menstrual cycles can provide useful information, but epilepsy does not always behave predictably from month to month.
The 2026 Epilepsia review raised an important issue: seizure patterns can occur over weeks or months independently of menstruation.
This means clinicians may sometimes need a longer record before being confident that menstruation is genuinely associated with the change.
A diary helps provide evidence rather than relying on memory alone.
What if periods are irregular?
Irregular cycles can make menstrual-related seizure patterns harder to identify.
A period may be considered irregular when the timing changes considerably from one cycle to another, periods become unusually infrequent, or expected periods stop.
Possible causes are numerous and include factors unrelated to epilepsy.
However, epilepsy itself and some antiseizure medicines may also be associated with reproductive or menstrual changes.
If periods become:
very irregular
unusually heavy
much more painful
very infrequent
or stop unexpectedly,
it is worth discussing this with a GP or appropriate specialist rather than assuming epilepsy is responsible.
Can epilepsy itself affect periods?
Possibly.
Epilepsy involves brain networks that can interact with systems controlling reproductive hormones.
Research has found increased rates of some reproductive and menstrual disorders in certain groups of women with epilepsy, although it can be difficult to separate the effects of:
epilepsy itself
seizure frequency
antiseizure medication
weight and metabolic factors
age
and other medical conditions.
This means menstrual changes deserve assessment in their own right.
They should not automatically be dismissed as "just epilepsy".
Antiseizure medicines and menstrual health
Some antiseizure medicines can affect hormonal or reproductive health.
Associations between valproate and menstrual irregularity, increased androgen levels and polycystic ovary syndrome have been reported, although not everyone taking valproate develops these problems and reproductive symptoms can have many causes.
Medication should never be stopped or altered without specialist advice.
Current UK prescribing rules around valproate are particularly strict because of its reproductive risks. People taking valproate who have concerns about periods, contraception or pregnancy should discuss them with their epilepsy team.
Periods, contraception and epilepsy medicines
Hormonal contraception introduces another layer because interactions can work in both directions.
Some antiseizure medicines can make certain hormonal contraceptives less effective.
NICE specifically notes medicines including:
carbamazepine
oxcarbazepine
phenytoin
and topiramate
as examples that can impair the effectiveness of some hormonal contraceptives.
Other enzyme-inducing antiseizure medicines can have similar effects.
At the same time, hormonal contraception containing oestrogen can reduce lamotrigine levels, potentially changing seizure control.
The exact interaction depends on the antiseizure medicine and the contraceptive method being used.
This is why contraception should ideally be discussed with a clinician or pharmacist who understands the person's epilepsy medication.
Related Information Hub page:
Contraception and Epilepsy — coming later
What about the contraceptive pill and periods?
Some hormonal contraceptives change bleeding patterns.
Depending on the method, periods may become:
lighter
less frequent
irregular
or absent.
That does not necessarily mean the underlying hormonal cycle has disappeared in the same way for every contraceptive method.
For someone tracking possible catamenial seizures, starting or changing hormonal contraception can therefore make the pattern more complicated to interpret.
Record the date a contraceptive method is started, stopped or changed and tell the epilepsy team if seizure frequency changes afterwards.
Does premenstrual syndrome affect seizures?
Premenstrual syndrome, or PMS, can cause symptoms such as:
mood changes
irritability
anxiety
disturbed sleep
headaches
bloating
tiredness
and changes in appetite.
Some of those factors — particularly poor sleep and stress — are also reported seizure triggers for some people.
So an increase in seizures before a period may involve several overlapping influences rather than reproductive hormones alone.
How is catamenial epilepsy diagnosed?
There is currently no single blood test, scan or EEG result that proves catamenial epilepsy.
Diagnosis is primarily based on demonstrating a reproducible relationship between seizures and the menstrual cycle.
A specialist may examine:
seizure diaries
menstrual records
usual cycle length
whether ovulation is occurring
seizure type
epilepsy syndrome
medication
and other possible triggers.
In some circumstances, hormone tests, ovulation testing or other investigations may be considered.
Research studies have often used an approximate two-fold increase in seizure frequency during a particular menstrual phase as a marker of a catamenial pattern, but diagnostic definitions remain inconsistent across the scientific literature.
Can catamenial seizures be treated?
Treatment is individual.
The first priority is usually to ensure that the person's underlying epilepsy treatment is appropriate.
A specialist may review:
antiseizure medicine
seizure control throughout the month
menstrual regularity
contraception
reproductive plans
and whether there is a clear high-risk part of the cycle.
For people with a predictable pattern, clinicians sometimes consider additional treatment during the higher-risk days.
Approaches described in clinical practice and research include intermittent use of medicines such as clobazam or acetazolamide, and various hormonal strategies.
However, the evidence supporting specific catamenial treatments remains limited.
A Cochrane systematic review found that available randomised trials were too small and limited to establish clear evidence for many commonly discussed hormonal treatment strategies.
Treatment therefore needs to be planned individually by an epilepsy specialist rather than attempted without medical supervision.
Should antiseizure medicine be increased before a period?
Not without specialist advice.
Someone who sees a predictable seizure pattern might understandably consider taking additional tablets around their period.
This can be dangerous.
Antiseizure medicines have specific dosing schedules and side effects, and suddenly increasing or reducing them may cause toxicity, loss of seizure control or withdrawal-related seizures.
If a diary shows a clear pattern, take that evidence to the epilepsy team and discuss whether treatment needs adjusting.
Does menstruation change seizure first aid?
No.
The basic first aid for a seizure remains the same whether or not it occurs during menstruation.
Follow the person's individual seizure care plan where one exists.
Emergency help should be sought according to the same circumstances described in the Seizure First Aid page, including prolonged seizures, repeated seizures without recovery, serious injury, breathing problems or other reasons for concern.
Related Information Hub page:
Seizure First Aid
Privacy and dignity matter
A seizure occurring during a period can be particularly distressing.
Someone may experience menstrual bleeding alongside:
urinary incontinence
loss of bowel control
vomiting
sweating
confusion
or the need for assistance changing clothes.
Protect the person's dignity.
Avoid unnecessary attention from bystanders, cover them if appropriate, give simple explanations while they recover and allow them privacy once it is safe to do so.
The fact that someone has had a seizure does not remove their need for dignity or personal boundaries.
When should someone speak to their epilepsy team?
Consider discussing menstrual health with the epilepsy team if:
seizures repeatedly increase around a particular stage of the cycle
previously controlled seizures begin occurring around periods
seizure clusters repeatedly occur at the same point in the cycle
periods become irregular after starting or changing medication
hormonal contraception appears to change seizure control
pregnancy is being considered
there are concerns about valproate or topiramate
medication side effects are affecting menstrual or reproductive health
or seizure control changes substantially without an obvious explanation.
Bring a seizure and menstrual diary if possible.
Patterns written down over time are often easier to assess than trying to reconstruct several months from memory during an appointment.
Valproate and topiramate: important UK safety information
People taking antiseizure medication should not stop treatment because of information they read online.
However, there are specific UK safety measures concerning some medicines.
Valproate
Current MHRA guidance states that valproate should generally only be started in someone under 55 when two specialists independently agree that other treatments are ineffective or unsuitable, or that reproductive risks do not apply.
Women and girls who could become pregnant must meet the requirements of the Pregnancy Prevention Programme when valproate is used.
Valproate should not be stopped suddenly without specialist advice.
Topiramate
Topiramate also has a Pregnancy Prevention Programme because exposure during pregnancy is associated with significant risks to an unborn child.
Current MHRA restrictions apply to women and girls who could become pregnant, with specific exceptions and requirements depending on why topiramate is prescribed.
Anyone concerned about these medicines should contact their epilepsy specialist, GP or pharmacist rather than stopping treatment themselves.
The most important message
Periods do not affect everyone with epilepsy in the same way.
Some people experience a clear and repeatable increase in seizures at particular points in their menstrual cycle.
Others notice occasional fluctuations that turn out to be related to sleep, stress, medication or another factor.
Many notice no menstrual relationship at all.
The best way to investigate a suspected pattern is to record rather than assume.
Track seizures and menstrual cycles together, continue taking medication as prescribed and discuss recurring changes with the epilepsy team.
Menstrual health is part of epilepsy care and deserves to be discussed openly.
Sources and further reading
Epilepsy Action — Periods and catamenial epilepsy.
UK patient information covering menstrual cycles, catamenial patterns, diagnosis and treatment. Last modified November 2025.
NICE — Epilepsies in children, young people and adults (NG217).
Guidance covering treatment, reproductive health, contraception and antiseizure medication interactions. Last updated January 2025.
Maguire MJ, Nevitt SJ. Treatments for seizures in catamenial (menstrual-related) epilepsy. Cochrane Database of Systematic Reviews.
Systematic review examining hormonal and non-hormonal treatments for catamenial epilepsy.
Monthly or menstrual? A scoping review of catamenial epilepsy and non-menstrual seizure rhythms. Epilepsia. 2026.
Recent review examining definitions of catamenial epilepsy and the difficulty of distinguishing menstrual associations from other longer-term seizure rhythms.
Medicines and Healthcare products Regulatory Agency — Valproate: reproductive risks.
Current UK safety measures for valproate.
Medicines and Healthcare products Regulatory Agency — Topiramate Pregnancy Prevention Programme.
UK regulatory safety information for topiramate.
Epilepsy Action — Contraception and epilepsy.
Current UK information on contraception and antiseizure medicine interactions. Updated September 2026.
Information reviewed: September 2026.
This page provides general educational information. It does not replace individual medical advice from an epilepsy specialist, GP, pharmacist, gynaecologist or other healthcare professional.
