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Can Metformin cause odd periods?

Hi ladies, just wondering if anyone experienced odd or unusual periods after they started taking metformin?

I started taking it towards the end of January and I started having light spotting on the 7th March (my first period whilst on it). I had the spotting on the 7th and was brown in colour, on the 8th was slightly heavier but still only really spotting, same colour. On the 9th had the same amount of bleeding but red/fresh blood and had it again on the 10th but for the morning only, nothing in the afternoon, had a tiny bit of brown bleeding yesterday morning but nothing since.

This is really unusual for me and am a bit worried. I started taking clomid on the 10th and am on day 3 of taking it, it’s my first cycle on it.

Just wondering if anyone else has had the same thing?

Thanks x

4 Replies

Hi CaroMayberry. Hopefully now you've started the Clomid, it will sort things out. Just thought I would send my explanation about how Metformin works, so you will understand it better. I don’t know if you know much about how Metformin works, but I will explain as simply as I can, with apologies if you already know. People who are diabetic (I realise you are not) - are treated in 3 different ways – diet, tablets (Metformin) or insulin injections. Women who are not ovulating properly and/or do not have regular periods and who are sometimes overweight, are often prescribed Metformin. The reason being is that they often have an excess of insulin in their body cells. Because of this the glands in the brain that control ovulation, the pituitary and the hypothalamus cannot get their message through to the ovaries to get them to ovulate properly. Metformin “mops up” the excess insulin to allow the messages to get through. Often it can regulate periods, but ovulation still does not occur. This is when a drug called Clomid is often introduced as well to hopefully ensure ovulation occurs. Metformin allows Clomid to do its job more efficiently.

It all sounds very complicated, but the mechanics of the idea work well. Of course this treatment does not work with every woman, and there is always the possibility that IVF or similar treatments may be required. Diane


Hi Diane, thanks for this. I’m quite lucky as my PCOS isn’t as bad as it is for some, I have irregular periods but I do ovulate which I know is half the battle. My blood work as far as glucose levels and insulin go have always come back normal, blood pressure is also normal and I’m not diabetic and thyroid is also ok so that is good, I think with me starting clomid this cycle I’m panicking a bit. I’ve stsrted taking it now so hope I’m doing it all right, my periods when I do get them are usually quite heavy and last a full week but this has been the complete opposite. For most of last year my cycles were approx 30 days but since October/November they have started getting longer, last cycle was 41 days and the cycle before was 52. I have a slight fear of having to go down the IVF route so feel a bit of pressure I guess for this to work x


Hi. Hopefully the Clomid will regulate your ovulation and cycle. Try not to worry about it, you never know you may be one of the lucky ones where it happens first or second cycle. Thinking of you. Diane

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Thank you, I hope so too! We’ve been trying for so long 🤞🏻 X


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