# Caffeine, alcohol and your cycle

> Your coffee and cocktails, decoded

Category: Nutrition · 3 min read · Written by the Splash team · Sources checked October 2026
URL: https://splash.care/learn/nutrition/caffeine-alcohol

## Quick answer

- There is no good proof that caffeine causes PMS, but it can affect sleep, bloating and jitters.
- Heavier drinking is linked with more PMS, though that does not prove cause.
- No more than 14 units a week, spread out, with drink-free days.
- In pregnancy: no more than 200mg caffeine a day, and no alcohol.

You do not have to give up your morning coffee or a drink with friends. But caffeine and alcohol can nudge your [sleep](https://splash.care/learn/movement-sleep/sleep-cycle) and mood, which matters most in the days when [PMS](https://splash.care/learn/glossary/pms) is already making things wobbly. Here is what the research really says.

## Caffeine

ACOG advises avoiding caffeine for [PMS](https://splash.care/learn/conditions/pms). But the best study we have, following more than 1,200 women with a PMS diagnosis over many years, found that caffeine did not make PMS more likely. The NHS PMS page does not list caffeine either. So cutting out caffeine is not a proven PMS fix.

Caffeine does matter for sleep, though. The NHS says to avoid tea and coffee at least 6 hours before bed. It also lists caffeine in coffee and tea among things that can add to [bloating](https://splash.care/learn/body-literacy/bloating), and [IBS](https://splash.care/learn/glossary/ibs) flare-ups can be linked to it too. If you feel jittery or wired before your period, try keeping caffeine to the morning.

**200mg** Daily caffeine limit the NHS gives for pregnancy. A cup of instant coffee has about 100mg, tea 75mg, a can of cola 40mg

## Alcohol

**14 units** The most the NHS advises drinking in a week, spread over 3 or more days. It is called low risk, not safe

A 2018 review that pooled 19 studies found people who drink alcohol had a moderately higher chance of PMS, and the link was stronger for heavy drinking. That does not prove alcohol causes PMS. Some people may drink to cope with PMS instead. The NHS PMS page does say not to drink too much alcohol, and the NHS [period pain](https://splash.care/learn/period-care/cramp-relief) page says cutting down on alcohol may help with period pain.

Alcohol can also make [low mood](https://splash.care/learn/mind-mood/why-mood-shifts) and anxiety worse, and it disrupts sleep even if it makes you drowsy at first. The NHS says regular drinking at high-risk levels can make mental health worse.

- Have several drink-free days each week.
- Alternate alcoholic drinks with water or a soft drink, and drink more slowly, with food.
- A 175ml glass of 12% wine is about 2 units, and a pint of strong lager is about 3.
- If you could be pregnant or are trying to conceive, the NHS advises not drinking at all.

> **Splash says:** try a "swap week" before your period. Decaf after lunch and a fancy mocktail on Friday. Log your sleep and mood and see if you notice anything. Your own results matter more than a rule.

### When to see a doctor

Talk to a GP if you are relying on alcohol to cope with low mood or anxiety, or you find it hard to cut down. Drinkline is a free, confidential helpline on 0300 123 1110. If you drink a lot every day, do not stop suddenly without advice, as this can be dangerous.

## Sources

1. [NHS: PMS (premenstrual syndrome)](https://www.nhs.uk/conditions/pre-menstrual-syndrome/)
2. [Purdue-Smithe et al. (2016) A prospective study of caffeine and coffee intake and PMS, American Journal of Clinical Nutrition](https://pmc.ncbi.nlm.nih.gov/articles/PMC4962155/)
3. [Fernandez et al. (2018) Premenstrual syndrome and alcohol consumption: systematic review and meta-analysis, BMJ Open](https://pmc.ncbi.nlm.nih.gov/articles/PMC5905748/)
4. [NHS: Alcohol units](https://www.nhs.uk/live-well/alcohol-advice/calculating-alcohol-units/)
5. [NHS: The risks of drinking too much](https://www.nhs.uk/live-well/alcohol-advice/the-risks-of-drinking-too-much/)
6. [NHS: Alcohol support](https://www.nhs.uk/live-well/alcohol-advice/alcohol-support/)
7. [NHS: Foods to avoid in pregnancy (caffeine limits)](https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/)

This is general information, not medical advice. Splash can’t diagnose. If you’re worried, talk to a GP, pharmacist or sexual health clinic. In an emergency call 999 (UK) or 911 (US).