PMS or PMDD? How to tell the difference

By the Twilune team, checked against the sources below · October 27, 2026 · 6 min read

PMS and PMDD share many symptoms. The difference is intensity. PMDD is a more severe form of PMS, with symptoms that are much stronger and that get in the way of work, relationships and daily life. Only a doctor can tell you which one you have, and tracking your symptoms over at least two cycles helps them do it.

If you are having thoughts of harming yourself or ending your life, please do not wait. Contact your local emergency number or a crisis line now. In the US, call or text 988. In the UK and Ireland, call 999 in an emergency or Samaritans on 116 123. Elsewhere, Find A Helpline lists free lines by country. More detail is at the end of this article.

What is PMS?

PMS, or premenstrual syndrome, is a mix of physical and emotional symptoms that show up in the days before a period. The NHS lists mood swings, feeling low or irritable, tiredness, trouble sleeping, bloating, cramps, breast tenderness, headaches, and changes in appetite. The Office on Women's Health adds anxiety, trouble concentrating and food cravings.

Symptoms are different for each person and can change from month to month. They usually ease within a few days of your period starting. For a closer look at why this stretch of the cycle can feel harder, read why you feel different in your luteal phase.

What is PMDD?

PMDD stands for premenstrual dysphoric disorder. The NHS says its symptoms are similar to PMS but "much more intense." Cleveland Clinic describes anger, anxiety, depression and mood swings as the emotional symptoms, and IAPMD names anger, irritability, depression and anxiety as the prominent ones. The NHS adds that PMDD can also include joint and muscle pain, overeating, and sleep problems.

Like PMS, PMDD follows the cycle. Symptoms start in the one to two weeks before a period and ease within a few days of bleeding starting. IAPMD describes PMDD as a condition in which the brain responds abnormally to normal hormone changes, rather than one in which hormone levels are abnormal.

It is not very common. The Office on Women's Health says PMDD affects fewer than 5% of women of childbearing age. IAPMD describes it as around 1 in 20 people who menstruate. Other sources give different figures, so treat any single number as an estimate.

How can you tell PMS from PMDD?

An article cannot do this for you, but these questions point to the difference:

The Office on Women's Health says severe symptoms that interfere with work, school or daily life may point to PMDD, and that it is worth asking a doctor about it. The NHS suggests seeing a GP if lifestyle changes have not helped or if symptoms are affecting your daily life.

How is PMDD assessed?

There is no single test for PMS or PMDD. A doctor relies on your symptoms, your history, and when the symptoms happen in your cycle. Cleveland Clinic notes that other conditions, such as anxiety, depression or reproductive disorders, have to be ruled out too.

The formal criteria (called DSM-5) ask for at least five symptoms in most cycles over the past year, with at least one of them being a mood symptom. Symptoms should be present in the final week before your period and largely settle after it starts. According to a 2023 review in Frontiers in Global Women's Health, the criteria say the picture should be confirmed by daily ratings over at least two symptomatic cycles. The same review says that looking back from memory is more prone to false positives and overdiagnosis.

That is why tracking matters. It is something you can start today.

What should you track before you see a doctor?

The NHS advises keeping a symptom diary for at least two menstrual cycles and taking it to your GP. Cleveland Clinic says you can track on paper, a calendar or a phone app, and suggests bringing the start and end dates of your last two periods. Useful things to note:

• The dates your period starts and ends.
• Each day's mood, energy and sleep, and any physical symptoms.
• How strong each symptom was, on a simple scale such as 1 to 3.
• What the symptoms stopped you doing: work, plans, time with people.
• What helped, and what made things worse.

Twilune can log your period, flow, symptoms, moods, energy and sleep in one place, and the logs stay on your phone. After a couple of cycles it can show patterns by phase. It is not a medical device and cannot assess PMDD. What it gives you is a record to show a professional. Paper works just as well. The important part is writing it down each day instead of remembering later.

How do you talk to a doctor about it?

It can be hard to say "my mood falls apart before my period" and feel taken seriously. A few things can help:

1. Start with the effect: "For about a week before my period I can't work, or I snap at people I love, and it happens most months."
2. Show your diary instead of describing it from memory.
3. Say what you have already tried and whether it helped.
4. Ask what the options are and what the next step would be. The NHS lists lifestyle changes, CBT, hormonal medicines and antidepressants as options a GP may discuss, and referral to a specialist if symptoms continue. Which ones suit you is a decision for you and your doctor.
5. If you do not feel heard, you can ask for a second opinion or a referral to a specialist.

Bringing someone you trust can help. If they see you every month, they can say what they notice. If you want a partner to understand, our guide on how to support your partner during PMS is written for them.

What if you are having thoughts of self-harm?

PMDD can bring thoughts of suicide. The NHS says that if you have PMDD symptoms and feel suicidal, you should call 999 or go to A&E (in Ireland, 112 or 999). IAPMD also says PMDD can cause suicidal thoughts and behaviors, and Cleveland Clinic advises anyone with suicidal thoughts to get help right away.

You do not have to wait for a diary, a diagnosis or an appointment. Reach out now:

• Any emergency: call your local emergency number.
• United States: call or text 988, the Suicide & Crisis Lifeline. It is free, confidential and open 24/7 (988lifeline.org).
• UK and Ireland: Samaritans on 116 123, free and open every day of the year (samaritans.org).
• Other countries: findahelpline.com lists free, confidential lines by country.

If someone is in danger right now, stay with them and call emergency services. Twilune has an SOS screen with crisis lines. Calm tools such as 5-4-3-2-1 grounding and breathing exercises can steady a hard moment, but they do not replace help from a person.

What to remember

• PMS and PMDD sit on a spectrum. PMDD is the more severe end, with strong mood symptoms that disrupt life.
• Only a doctor can assess it. Tracking daily for at least two cycles gives them the clearest picture.
• You do not need a perfect diary before you ask for help.
• If you are thinking about harming yourself, contact a crisis line or emergency services now.

This article is general information, not medical advice.

Frequently asked questions

This article is general information, not medical advice. If something worries you, or your symptoms are severe or getting in the way of your life, talk to a doctor. If you are thinking about harming yourself, call your local emergency number now.