It's day 25, the dishwasher has been loaded wrong, and this is, apparently, the end of the world. You know it's hormonal. Knowing doesn't help at 7 pm. What does help is a short list of things with some evidence behind them, tried in the right order, set up before the week arrives rather than in the middle of it.
We covered the why in mood swings before your period: your hormone levels are normal, and it's your brain's response to the late-luteal drop that isn't. Here are nine things, roughly in the order we'd try them.
1. Track two or three cycles before you change anything
The most useful item here. ACOG defines PMS by pattern: symptoms in the five days before a period, for at least three cycles in a row, that end within four days of bleeding starting. A paper calendar with a one-word note per day ("fine", "weepy", "rage") tells you which days to plan around and whether anything below is working.
2. Keep the same wake time
Short sleep makes every mood symptom louder, and the luteal phase already trims your REM sleep. ACOG's advice is unglamorous: regular sleeping habits, waking and going to bed at the same times every day including weekends, may lessen moodiness and fatigue. We'd add: same wake time even after a bad night. The lie-in feels like recovery and mostly moves the problem to the next day.
3. Move, and start before the mood week
A 2020 meta-analysis in BJGP Open pooled randomised trials and found that at least eight weeks of regular exercise cut overall PMS scores, with the psychological symptoms among the clusters that moved most. The trials were small and many were at high risk of bias, so hold the size of the effect loosely. Eight weeks is the key number: this is a habit you build in the good weeks, not a fix you reach for on day 25.
4. Calcium, 1,200 mg a day
The largest nutrient trial for PMS we know of is a 1998 study of 466 women who took 1,200 mg of calcium a day or a placebo for three cycles. By the third cycle the calcium group reported substantially lower luteal symptom scores, and mood swings were among the 17 symptoms measured. ACOG now says the same: 1,200 mg of calcium a day can help reduce the physical and mood symptoms of PMS. Yogurt, tofu and leafy greens count towards it.
5. Vitamin B6, and not more than 100 mg
A 1999 systematic review in the BMJ pooled nine placebo-controlled trials covering 940 women and found that B6 at up to 100 mg a day was likely to help premenstrual symptoms, with the clearest signal on depressive and mood symptoms. The authors called the trials poor quality, and they were right. Stay at or under that dose; high doses over long periods have been linked to nerve damage.
6. Magnesium from day 15 to your period
A 1991 double-blind trial gave 32 women with PMS either magnesium or a placebo three times a day from day 15 of the cycle until bleeding started. Over two cycles the magnesium group reported significantly fewer premenstrual mood changes. Small and old, but ACOG lists magnesium among the supplements that may help mood symptoms, alongside bloating and breast tenderness. Pumpkin seeds, almonds, beans and dark chocolate are the food route.
7. Chasteberry, with a pharmacist's blessing
Vitex agnus castus is the one herb with a decent trial behind it. In a 2001 BMJ trial, 170 women took a chasteberry extract or a placebo daily for three cycles, and the chasteberry group reported a larger drop in irritability, mood alteration, anger and headache. It acts on hormone signalling, so if you're on hormonal contraception, fertility treatment or any psychiatric medication, ask a pharmacist before starting it.
8. Move the coffee earlier and skip the wine
ACOG's PMS guidance is blunt: avoid caffeine and alcohol. We'd settle for timing. In a 2013 trial, 400 mg of caffeine taken six hours before bed cut total sleep by more than an hour, and lost sleep is item 2 coming back to bite. Alcohol does the same to sleep and adds a low mood the next day. In the mood week, one coffee before noon and no evening drink is a cheap experiment.
9. Say what week it is
No trial for this one, just us. A text to your partner or flatmate on day 22 ("mood week incoming, not you") changes the next five days more than any supplement on this list. It stops you spending Thursday apologising for Wednesday. Our luteal phase self-care checklist has the rest of the week's plan.
This week is also why Girl Chocolate exists. We're a small team who have periods, and we make a dark chocolate bar for the days around your period, with magnesium and other functional ingredients, sold as a pouch of 8 bars to cover one cycle. It supports mood swings* in the same small, one-thing-among-nine way the food above does, and it's the thing we reach for on day 25 instead of the biscuit tin. The Period Type quiz helps you find which days you'll want it.
What did nothing for us
We tried a strict no-sugar luteal week, on the theory that steady blood sugar would mean steady mood. We were not calmer. We were hungry and exactly as irritable. If the week before your period regularly wrecks work or relationships, that's PMDD territory, and item 1 above is what gets you a proper diagnosis rather than another list.
Print our free PMS week meal plan: five days of meals built from calcium and magnesium foods, plus a grocery list. 1 page, PDF, no email needed.
Download the PDFSources
- ACOG, Premenstrual Syndrome (PMS) FAQ
- Pearce 2020, Exercise for premenstrual syndrome, meta-analysis (BJGP Open)
- Thys-Jacobs 1998, Calcium carbonate and the premenstrual syndrome, 466 women (Am J Obstet Gynecol)
- Wyatt 1999, Efficacy of vitamin B6 in the treatment of premenstrual syndrome, systematic review (BMJ)
- Facchinetti 1991, Oral magnesium successfully relieves premenstrual mood changes (Obstet Gynecol)
- Schellenberg 2001, Agnus castus fruit extract for premenstrual syndrome, randomised placebo controlled study (BMJ)
When to talk to a doctor
Mood swings that lift when your period starts are common. Book an appointment if:
- the week before your period regularly stops you living your normal life, or you have thoughts of harming yourself
- you bleed through a pad or tampon every hour
- pain suddenly got much worse than your usual
- you have pain with a fever
* These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
