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what causes black blood
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Hematologic Diseases
Question #15688
45 days ago
84

what causes black blood - #15688

Karthik

I am really worried because I’ve been noticing something strange. Last week, I felt super tired after a long day at work, and when I checked my blood after a minor cut, it looked really dark, almost black. I mean, like, what causes black blood, right? I didn’t think much of it at first, but then the next day, I just happened to see it again when I accidentally scraped my knee while running. I can’t remember ever seeing blood that dark before. Is it normal to have blood look like that? I’ve heard mixed things about what causes black blood — is it something serious? I did some googling and read that it could be due to oxygen levels or even some kind of poop blood?! Ugh, how awful is that? Is there a chance it could just be, like, totally nothing to worry about or does it mean there’s something wrong inside me?? I mean, should I rush to a doctor or can I just chill out and see if it happens again? It's super weird and I'm freaking out a bit. I just wanna know what causes black blood, any insight would help!

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Doctors’ responses

Seeing blood that appears very dark, almost black, can definitely be unsettling. Typically, the color of blood can range from bright red to dark red depending on its exposure to oxygen. Blood that is bright red is usually well-oxygenated, while darker blood can indicate it has less oxygen. When blood is exposed to air, it can appear darker. However, if you’re actually describing black-appearing blood outside of the context of menstrual blood or gastrointestinal bleeding, which are different scenarios, there may be less common and benign reasons, like lighting conditions or how quickly the blood oxidized. Occasionally, the lighting or angle can make dried blood appear much darker.

Still, let’s consider what’s concerning: black blood in the context of menstrual blood is usually due to it being older and having been in the body for longer before being expelled. In the gastrointestinal system, such as in stools, black blood can be a sign of bleeding higher up, where the blood digested turns black (melena), which definitely require immediate medical attention. Therefore in the scenario you described, if the dark color was noticed from a superficial cut or scrape and not related to menstrual or any internal symptoms, it is less likely to be concerning, but it’s tough to say for certain without seeing it. If it continues or there’s any other change like unusual fatigue, dizziness, or changes in stool or urine color, these should prompt a visit to a healthcare provider. Keep in mind significant fatigue could also be a symptom worth checking out. Best course of action would be to get a professional opinion if this continues or if you notice other symptoms, to ensure there’s no underlying issue such as anemia or circulation problems - which a doctor could help sort out with blood tests or further evaluation.

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