In The Walking Dead (as opposed to the book World War Z, for instance), it has been consistently shown that zombies have red, liquid blood, apparently indistinguishable from human blood.

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But we know that zombies are dead, and their circulatory system is no longer functional. As such, one might be forgiven for assuming that their blood would have coagulated shortly after they died - which is precisely what happens when a person dies in real life. In the aforementioned World War Z novel by Max Brooks, zombies have thick, solid, black, congealed blood, much like a dead human being does.

Why do the zombies on The Walking Dead retain their liquid blood? Shouldn't a person's blood coagulate upon death, and remain coagulated after reanimation?

  • Related: biology.stackexchange.com/questions/40213/…
    – Wad Cheber
    Commented Nov 2, 2015 at 21:55
  • Because they're not zombies, but Walkers? Commented Nov 3, 2015 at 1:15
  • @Paulster2 - Kirkman refers to them by both names out of universe and in the comics. Zombies are walkers and vice versa, but the word "zombie" doesn't exist in the television universe.
    – Wad Cheber
    Commented Nov 3, 2015 at 1:16
  • Sorry, Wad, I was just being flippant. Commented Nov 3, 2015 at 1:17
  • @Paulster2 - Ah. My bad. The whole "humorous intent is hard to detect on interwebs" problem.
    – Wad Cheber
    Commented Nov 3, 2015 at 1:19

2 Answers 2



DIC is an effect of some Hemorrhagic viruses; basically it causes mini-clots which deplete platelets and have the net result of reducing blood's ability to clot. There are many enzymes and chemicals that could keep blood liquid for a long time; I chose the above simply because it is something real-world viruses are definitely capable of. It doesn't explain why zombies only need a brain to keep moving; but it is plausible that DIC, or a related viral mechanism, could keep the contents of their skull wet and splatter-able...


It's established in S01E06 "TS-19" that zombies in The Walking Dead are, as Miracle Max might put it, only mostly dead. They're shown as having brain activity, mostly centered in the cerebellum (which controls heartbeat), so it seems possible that your assertion "we know... their circulatory system is no longer functional" is inaccurate and their blood is kept liquid by some modicum of continuing circulatory function.

  • Since they don't seem to notice when their heads are lopped off, I think it's safe to say that their hearts don't do anything useful. They also don't breathe, so circulation would be pointless as well. Shane riddled a zombie's chest with bullets, specifically saying "That's its heart, its lungs - why is it still coming?" The only logical answer to his rhetorical question is "because the heart and lungs aren't doing anything".
    – Wad Cheber
    Commented Nov 2, 2015 at 21:30
  • More to the point, in the same episode you mentioned, Jenner makes it quite clear that the person dies - really and truly dies. Blood begins to coagulate almost immediately upon death, and I don't see any reason to believe that the coagulation process would be, or even could be, reversed.
    – Wad Cheber
    Commented Nov 2, 2015 at 21:34

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