The context is someone is injured and is bleeding. Does “we need to stop the blood” sound right instead of “…stop the bleeding”?

Stop the bleeding. Which is also an idiom as well, like when something is going poorly, maybe a business is being badly run - you need to “stop the bleeding” - IE stop additional bad things from happening

It's mildly weird, 'stop the bleeding' is better.

No

“Stop the blood” sounds like the blood is already out of the body and we don’t want it to go further. “Stop the bleeding” means the blood is still in the body and we want to help keep it that way.

No

*we need to stop the blood...from coming out* That'd be a forced way to say it, if you had no way of saying *bleeding*

Even if it's not what people would necessarily say, you would be understood in the context of someone actively bleeding. I don't think a native speaker would be asking you to clarify what you mean.

Technically you are stopping the blood from leaving the body, but the phrase is "stop the bleeding" because bleeding is an action.

No, it doesn't. Stop the bleeding is better. In fact, I'd say "stop the blood" would only be technically correct.

"Stop the blood" doesn't sound *too* bad, and people would understand you, but it's not as natural as "stop the bleeding". To "stop" something can also mean to block an opening so liquid can't get through, like putting a cork in a bottle or repairing a leaky bucket. So "stop the blood" kind of sounds like you mean "plug the hole" rather than "encourage clotting". 🥲

It sounds stupid

Blood is a noun, bleeding is a verb, seeing as bleeding is an action it can be stopped.

You can't stop the blood but you can stop the bleed. The bleed being a noun for the act of bleeding.

Technically it isn't quite right, but in context we'd understand that you mea something like "We need to stop the blood *from continuing to leave their body.".* I can easily imagine that many native speakers (especially if they are panicking) could make this small error if faced with an emergency in real life, since we might not be thinking 100% clearly, or our thoughts might not properly translate to words.

It's "stop the bleeding." We're stopping the action of blood coming out, which is "bleeding."

It would be weird in a medical drama but I can see it being used in a thriller or detective scenario. A little non-standard but would indicate that people are under stress and potentially starting to panic.

“Stop the blood” only works in a dungeons and dragons universe where the blood is turning into a monster to kill you. Alternatively there could be some circumstances where you want to stop the movement or shipment of blood. Say you are a doctor doing an infusion and you want the nurse to stop pumping blood in. But if blood is coming out of your body, that’s always stop the bleeding.

Stop the bleeding

Blood is just blood. It’s not doing anything. To stop the blood doesn’t mean anything. When someone is injured, they’re bleeding. That’s why, in that context ‘stop the bleeding’ is better.

It's understandable but it's not what a native speaker would say.