Endometriosis UK
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coming to end of cycle and thin black/brown blood

hi all can anyone help im coming to the end of my cycle and i have noticed like thin black brown blood never had it before plus the pains in my groin which have started to travel up towards my rib cage also my boobs are VERY swollen and sore the blood is new the other symptoms have been going on for the last two months any help im more than greatfull im getting concerned something is wrong

6 Replies

Hiya Sully,

I had this at the beginning of my period, I know it's the opposite way round. I don't know if it makes a difference when it occurs for there to be diagnosis of endo or not, but from a lot of sites it seems a common symptom. Apparently from what I've read it's old blood from the endo reacting to the bodies cycle?! As I've said its only what I've read so I'd check with your doctor just in case it could be related to something different in your case. Hope this helps you out a bit.


Please don't worry, all old blood or old menstrual lining turns really dark when it has been there a while, just like a scab on the skin will turn much darker than a bright red fresh bleed. All it means is that the oxygen has gone and this could be because it might be left over from the previous month's bleed and is only now able to shed away and escape. Nothing AT ALL to worry about. Not related to endo or anything sinister. As you get older this happens more and more with your periods. If you are on the pill or any drugs to delay or stop you having a period that lining hangs about inside a lot longer than normal and will stop being the bright red fresh bleed colour. You might get both happening at the same time, old dark lining shedding and behind it a fresh wound releasing bright red blood. But also sometimes the old lining did shed off last month, but didn't escape till this month, and there won't be any fresh blood to go with it. Hope that makes some sense.

If you have endo then the old trapped blood inside you (usually in the Pouch of Douglas) or in an endometrioma cyst, will turn darker chocolate coloured which is why the endometrioma cysts are called chocolate cysts. Simply means the blood is old and drying up and looks like dark chocolate in colour. If you have a nose bleed on a pillow or your shirt, it doesn't stay a red stain, soon turns brown when the oxygen is gone from it.


Pain in boobs is caused by changes in your sex hormone levels..can be due to drugs interacting with the ovaries, or having an ovarian cysts can also play havoc with the hormone levels and give your sore boobs too. If you are checked and don't have a cyst, then you might want to try controlling the hormone fluctuations with BC pills- many to try-all have slightly dif combinations of hormones so it is a trial and error to find one that suits you best and gives the last side effects. If one doesn't suit then switch to a another kind and see how you get on. Do visit the GP about your sore boobs- something can be done to try and reduce the discomfort for next month. But the colour of blood issue is nothing to worry about although it does look pretty horrific when you are used to bright red.


Hi there, I had an ovary and fallopian tube removed due to a large endometrioma earlier this year caused by undiagnosed endo (took 18 months to finally get a diagnosis and treatment but thats another story!!). Since my endo worsened I get the same thing, sometimes its like tar (sorry waaay TMI!!!), my consultant said it is old blood but is part of endo too (especially the tarry stuff). It goes on and on I only get about 10 days where everything is clear, but dont worry it isnt anything nasty xx



I'm the same as ermintrude 38. Had my left ovary and choccy cyst removed last year. Had tarry like blood before this and now again after my surgery. I am currently on cerezette, mirena coil, decapeptyl and had a womb ablation, but the bleeding still continues. This month I have had the brown stuff approx 11 days out of the last 14 days and also a full red period for 1 day. Now I have a pinky show this morning and it looks like Im about to get another period. I think this is all normal with Endo, but u can also get brown blood by having the mirena coil too. I know it doesn't look very nice, but it seems to b the way Endo just works. If ur not on any hormone treatments then maybe ur GP could check ur hormone levels for u? xx


thank you everyone im on no treatment for my endo at the min and im not allowed the pill due to estrogen and mini pill i constantly bleed with no break i thought i might have a cyst due to the new pain which i manage with tramadol i will go to my gp about my boobs as they are driving me mad i don't mind them being larger lol but they do get sore to the point putting my bra on i cry sometimes


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