PMS vs PMDD: how to tell the difference

(with a bit of my personal story)

For years I went back to my GP almost every month because, in the week before my period, I felt like I didn’t want to be here anymore. The pressure in my chest built and built. Lights felt too bright. Some nights I couldn’t sleep at all; other days I couldn’t get out of bed. At my worst, I felt like I could hear or see things that weren’t there.

That wasn’t “just a normal period.” It was PMDD.

What helped me turn a corner was using every tool available: proper medical support (including a period of time on fluoxetine), therapy, and simple but consistent nutrition and lifestyle changes. I’m here because of that combination, and it’s exactly the approach I encourage for my clients too.

PMS vs PMDD – what’s the difference?

Lots of us get some premenstrual symptoms (PMS): feeling a bit lower, tired, crampy, irritable. Unpleasant, yes — but still manageable.

PMDD (Premenstrual Dysphoric Disorder) is different. It’s a severe form of premenstrual symptoms that can affect your mood, your relationships, your work, and your ability to cope. The key things to notice are timing and impact:

• Timing: symptoms ramp up in the week or two before your period and usually ease once your period starts.

• Impact: PMS is uncomfortable; PMDD can be overwhelming, with big mood swings, hopelessness, anger, anxiety or panic, and a sense that you’re not yourself. It can make everyday life feel impossible.

  
  

If you recognise yourself in that, you’re not being dramatic and you’re not weak. You’re having severe symptoms that deserve proper care.

A quick self-check

If several of these feel true for you, speak to your GP:

• Your hardest days are reliably right before your period, then lift soon after bleeding starts.

• Your mood changes feel extreme (e.g., despair, rage, anxiety, feeling out of control).

• It gets in the way of work, studies, relationships, or basic self-care.

• You notice clear “good weeks” and “bad weeks.”

• You’ve kept a simple daily symptom log for a couple of cycles and can see the pattern.

  
  

PMDD can also sit alongside other things like anxiety or depression. Tracking helps your GP see what’s cyclical and what isn’t.

Getting help and a diagnosis.

Start with your GP. Take two months of daily notes (an app like Flo/Clue works, or a simple paper tracker). You don’t need fancy tests — the pattern you show your GP is what matters most.

Your GP may suggest options such as:

• Medication (for many people, an SSRI like fluoxetine is life-changing; sometimes taken just in the luteal phase).

  
  

• Talking therapies (CBT or similar).

  
  

  They’ll also check for things that can make symptoms worse, like low iron or thyroid issues.

A gentle reminder: medication can be life-saving. Nutrition is a powerful support, but it doesn’t replace medical care.

What you can do with food and lifestyle (the simple version)

These are the steady, boring basics that move the needle. Start here and keep them going — especially in the two weeks before your period.

1. Eat protein at every meal

   
   

   Helps steady energy and mood. Think eggs, fish, chicken, tofu/tempeh, beans, lentils, Greek yoghurt. Aim for a palm-sized portion.

   
   

2. Build your plate with fibre and plants

   
   

   Your gut and brain are connected. Go for leafy greens, colourful veg, beans, pulses, wholegrains, nuts and seeds. Aim for a couple of handfuls of veg at lunch and dinner.

   
   

3. Magnesium, little and often

   
   

   Foods rich in magnesium can help with mood, sleep and cramps: pumpkin seeds, leafy greens, cocoa/dark chocolate, beans, oats. Many people also do well on a magnesium supplement — ask your pharmacist or clinician what’s right for you.

   
   

4. Omega-3s and B-vitamins

   
   

   Add oily fish (or chia/flax if plant-based) a couple of times a week, and include foods with B-vitamins (eggs, wholegrains, potatoes, pulses).

   
   

5. Rhythm helps

   
   

   Gentle movement you actually enjoy, daylight in the morning, winding down at night, and keeping caffeine/alcohol modest — especially in the luteal phase.

   
   

Extras I sometimes use with clients (case-by-case)

• Cruciferous veg (broccoli, kale, sprouts, cabbage) most days to support overall hormone balance within a healthy diet.

  
  

• Herbs like saffron can help some people, but always check for interactions if you’re on medication.

  
  

• Private tests can occasionally help personalise a plan, but they don’t diagnose PMDD. The only “test” that really matters is your symptom diary.

  
  

Please don’t gaslight yourself

If you’re feeling unsafe, unable to function, or like a different person every month, that’s not because you aren’t strong enough. We’re juggling a lot — modern stress, poor sleep, screens late at night, caring responsibilities, under-eating protein, skipping meals — it all adds up.

Many of my PMDD clients also discover neurodiversity later in life; understanding that can make everything make more sense.

Urgent help (UK)

Need to add this, but if you feel unsafe, are having suicidal thoughts, or can’t keep yourself safe, this is not your fault and it is not “just PMS.”

• Samaritans: 116 123

• NHS 111 for urgent advice

• 999 in an emergency

  
  

Next steps

• Start tracking today. A simple 1–10 rating for mood/sleep/energy each day for two cycles is enough.

• Book your GP appointment and take your tracker.

• If you’d like nutrition support alongside clinical care, you can book a discovery call with me.

• Or download my PMS Starter Kit (it's on my website pop-up) and try the 7-day basics.

  
  

Message me or reach out with any comments; I'm always happy to hear from you.

Catherine xx

PMS 7 DAY STARTER KIT (WEBSITE POP UP)