In Let's Kill Hitler, an episode from the 11th Doctor, the Doctor and his companions encounter the usual assortment of difficulties and obstacles.

However, the biggest difficulty contains something that I don't quite understand.


When Melody Pond kisses the Doctor, she doses him with a poison via the kiss. Apparently this poison somehow "prevents regeneration".

How is this possible? Is there any precedent for this being achievable in other episodes (including prior to the series reboot)?

3 Answers 3


He's poisoned in "The Unicorn and the Wasp" with cyanide, but is able to detoxify himself, so it has been established that he can be poisoned. There's really no reason to assume he can't be poisoned at all. While Timelords can regenerate, they are still biological, which means chemical reactions occur within their bodies, so it would be quite possible to introduce a substance that upsets their chemical processes and results in death.

The Third and Tenth Doctors have to regenerate because they're dying from radiation poisoning.

The Fifth Doctor is forced to regenerate due to spectrox toxaemia poisoning, which happens in "The Caves of Androzani."

Since regeneration is also a process that ties in with their biology, there's no reason to assume that it's impossible to find a chemical or combination of chemicals that could impede that function, just as we use chemicals to impede functions in our bodies.

  • 2
    There isn't really any doubt as to whether the Doctor can be poisoned (I chose that title simply to avoid spoilers). The question is really about whether a simple chemical compound can "block" the regeneration effect (which you address in the last paragraph).
    – Beofett
    Sep 20, 2011 at 15:55
  • 2
    I felt like I needed to include the first and build to the last -- just for completeness and to avoid someone saying, "But are you sure he can be poisoned?" I saw what you were asking, but felt I should include that background first. I suppose I should have pointed that out.
    – Tango
    Sep 21, 2011 at 1:21
  • Since the entire process of regeneration itself is pretty poorly understood, the writers can make up pretty much any rules about it that they like. And if any non-Gallifreyan would know how to block regeneration, it would be River's employers. Jan 10, 2012 at 14:06
  • Frankly the answer is self-evident: it's "yes", because we saw it happen, in the event you're asking about. Jun 12, 2014 at 22:52
  • @Beofett is it stated to be a simple chemical compound? It could easily have a time-active component, or even something as vulgar as nanomachines.
    – evilsoup
    Jun 13, 2014 at 10:40

The TARDIS never actually says it's because of the poison.

HOLO-AMELIA: Your system has been contaminated by the poison of the Judas tree. You will be dead in thirty two minutes.

DOCTOR: Okay. So, basically better regenerate, that's what you're saying.

HOLO-AMELIA: Regeneration disabled. You will be dead in thirty two minutes.

Regeneration was "disabled" because he didn't have any regenerations left.

  • 2
    This is the correct answer. The Doctor couldn't regenerate. He was out of regenerations. I think it's sheer luck that the episode was written this way and that the dialogue can just about be interpreted in this way, because I'm fairly certain that the War Doctor hadn't yet been conceived of yet by the writers and, even if he had, they couldn't give that secret away so early with an obvious hint here. In fact, you've hit the nail on the head because just recently I was wondering why he even considered regeneration in this episode. This is why. He didn't. The wording is very clever. Jun 12, 2014 at 22:53
  • Nice catch there, the writers are probably spurting out their drinks going "shit, did we just do that?"
    – Memor-X
    Jun 12, 2014 at 23:08
  • Interestingly, this also gives new perspective on his 'Death' at Lake Silencio; it had to be faked, from the beginning -- he couldn't have started, and been stopped from regnerating... as he had no regenerations left by that point.
    – K-H-W
    Jun 12, 2014 at 23:56

I do not recall something like this ever happening in the Doctor Who universe. Bear in mind that the universes' continuity tends to be. . . well wibbly-wobbly timey-wimey. E.g. the "Tardis Scoop" performed by Ecceleston's Doctor at the end of that season (in Parting of the Ways, I believe) was un-precedented. It's not uncommon for something totally new to happen because a Writer needs it to/can't come up with an alternate way of writing something.

  • 1
    There is precedent for weapons-which-prevent-regeneration in general, though, and there's no reason to suppose someone who knew enough about Time Lords couldn't develop an appropriate poison.
    – Tynam
    Dec 18, 2011 at 18:09

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