Irregular periods are common and often have a simple explanation, such as stress or a recent change in contraception. Sometimes they point to a condition that is worth treating. The most useful thing you can do is keep a clear record, because it helps a healthcare professional find the cause faster.
Common causes of irregular periods
| Cause | What you might notice |
|---|---|
| Stress, illness or travel | One or two unusually long cycles |
| Big changes in weight or intense exercise | Longer cycles or missed periods |
| Stopping hormonal contraception | Irregular cycles for a few months |
| Polycystic ovary syndrome (PCOS) | Infrequent periods, sometimes acne or extra hair growth |
| Thyroid problems | Changes in cycle length, tiredness, weight changes |
| Perimenopause | Cycles that become shorter, longer or skipped from your 40s |
| Breastfeeding | Periods that stay away or return irregularly |
This table is not a diagnosis. Only a healthcare professional can find out what is behind your pattern.
When to make an appointment
Book an appointment if your periods stop for three months or more and you are not pregnant, if cycles are regularly shorter than 21 or longer than 35 days, if you bleed between periods or after sex, or if irregular periods come with severe pain, very heavy bleeding or symptoms such as excess hair growth.
What a doctor may ask
Being ready for these questions makes the visit more productive:
- When did your last few periods start, and how long did they last?
- How long have your cycles been irregular?
- Have you changed contraception, medication, weight or exercise recently?
- Do you have other symptoms, such as pain, acne or tiredness?
- Could you be pregnant?
The doctor may suggest a pregnancy test, blood tests for hormones or thyroid function, or an ultrasound, depending on your situation.
How to prepare in three steps
- Write down the start dates of your last six periods, or as many as you have.
- Note your shortest and longest cycle and how many days you usually bleed.
- List any symptoms and life changes, with approximate dates.
Our Try our free period calculator can help you work out cycle lengths, and our PCOS symptom checker is an educational list of common signs, not a diagnosis.
Keeping the record in Bloom Private
Bloom Private shows your cycle history with your shortest, longest and average cycle, lets you log more than 60 symptoms and notes, and creates a free basic PDF report to bring to your appointment. There is no account and no server: your records stay on your iPhone, protected by iOS encryption, unless you choose to export them or turn on Apple Health.
Frequently Asked Questions
Stress, illness, weight changes, intense exercise, stopping hormonal contraception, PCOS, thyroid problems, breastfeeding and perimenopause are among the most common.
If your periods stop for three months and you are not pregnant, if cycles are regularly shorter than 21 or longer than 35 days, or if you bleed between periods or have severe pain.
The start dates of your last periods, how long you usually bleed, your shortest and longest cycles, and any symptoms or life changes.