I started metformin for PCOS a month ago

Call your prescriber's office today and ask for a review — four weeks in on a new medicine, with barely a bowel movement for three weeks, is the point to ask rather than to keep pushing at home.

On your first question: metformin is well known for upsetting the gut, and the NHS patient page lists nausea, vomiting, diarrhoea, tummy pain, loss of appetite and a change in taste as the common effects, with most easing after a couple of weeks but some lasting longer (nhs.uk/medicines/metformin, checked 18 October 2026). Constipation is not on that common list, so I can't tell you it's simply the drug — that's your prescriber's call, not a home one. Don't stop or change the metformin on your own; the same page says keep taking it unless you're advised to stop.

1) What you've already tried, and the better levers

Adding laxative after laxative on your own is the part I'd stop. Stacking products without a plan means nobody knows what's in your system, and it can make things worse rather than better. Instead, tell the prescriber exactly what you've used, how much, and how long — that list is one of the most useful things you can bring them.

Inside the house, with what you already have:

• Food timing. The NHS page says most people take metformin with food. Attach each tablet to the meal it belongs to, and keep it there even on the school-run days. A stable routine is easier to defend than a rescue plan.
• A ten-minute walk after a meal. Once a day, with the school run or a neighbour's dog. Movement is the cheapest lever there is.
• Position on the loo. Feet on a low stool so knees sit above hips, elbows on knees, five to ten minutes, no straining, and get off the seat when nothing happens. Ten minutes on the loo is a limit, not a session.
• Fluid attached to places you already stand. A bottle on the kitchen table, one in the school-run bag, one at the desk. Water next to the meal, not "remember to drink later".
• Fibre you already buy — slowly. Oats, beans, lentils, pears, kiwi, prunes, brown rice. Add a little every few days, not all at once. If a food reliably makes the bloating worse, drop it and tell the prescriber; with this few bowel movements, a sudden fibre jump can make the pressure worse.
• Alcohol. The NHS page advises limiting alcohol while on metformin.
• B12. The same page lists vitamin B12 deficiency as a known effect, which shows up as heavy tiredness. Ask the prescriber whether they want it checked — don't start a high-dose supplement on your own.

2) Constraints — the avoid list

• No stopping, halving, doubling or swapping the metformin on your own, and no switching to a bought "extended-release" version. That choice, including whether a slow-release form fits you, belongs to the prescriber.
• No more open-ended laxative stacking, and no magnesium or fibre products you've not told the prescriber about.
• No powders, drops, or "detox" products bought online or from a market. Nothing unlabelled goes in while you are waiting to be seen.
• No prescriptions bought from online sellers.
• Nothing inserted into the rectum to force a movement, and no holding a swollen belly to "push it along".
• Don't let this eat the whole evening. Choose one lever per day, not six.

3) Decision tree — when to stop the home fixes

Go to an emergency department or call your local emergency number now if any of these are true today:

• Severe belly pain, or a belly that is hard, rigid, swollen or too sore to touch
• Repeated vomiting, or vomiting that is green
• Blood in the stool, or black, tarry stools
• A swollen belly that is getting bigger, or you cannot pass wind at all
• Fainting, dizziness when standing, confusion, or new drowsiness
• Fever together with belly pain
• Breathing deep and fast, or severe muscle cramps with vomiting and tiredness — the NHS page lists these as the signs of a rare but serious reaction to metformin
• Severe difficulty breathing or chest pain
• Any chance of pregnancy together with pelvic pain

If none of those, this is a call-your-prescriber-today situation, not an ambulance. Give it until the next working day, and if it turns into any line above, stop waiting.

The one question that decides this turn: have you had any vomiting, blood or black stool, a swollen or hard belly, or severe pain — yes or no?

Screenshot script for the call:

> "I've been on metformin for PCOS for about four weeks. For the last three weeks I've barely passed a stool. I've added magnesium, extra fibre and lots of water without much change, and I've been stacking laxatives on my own, which I'd rather stop. I'd like a review of the plan rather than another month of the same. Could we talk about whether a slow-release form would suit me better, and whether anything needs checking?"

Take the metformin packet with you, plus a short note: last real bowel movement, any laxatives or supplements used and since when, any pain, and whether you've had vomiting or blood.

What "success" looks like in 24 hours

Not a cure, and not a promised bowel movement — three weeks is a real problem and it may take a prescription change to move it. What success looks like tomorrow: you have spoken to the prescriber or have an appointment in hand; you've stopped stacking laxatives; and your belly is softer and less bloated than today, with you passing wind. If it's not softer by tomorrow, that's information for the appointment, not a reason to buy something new.

If you'd rather I point you at the right local door, tell me your country and city and I'll check it. What I can't do here is diagnose this, change your medication, or calculate a dose — the prescriber does all three.