The Harry Potter wiki says:

The effects of a single dose last anywhere from ten minutes to twelve hours, depending on how well the potion has been brewed.

But it doesn't say anything about how much has to be drunk.

In Harry Potter and the Deathly Hallows, several people drink from the same flask of Polyjuice Potion in order to transform into a decoy Harry. This would imply that the required dose is pretty small.

But in Harry Potter and the Goblet of Fire, Madeye Moody (actually Barty Crouch Jr. in disguise) runs out of potion before he meant to (he ransacks his stash but all the bottles are empty). So apparently he drank quite a bit.

So, how much do you have to drink? Could Moody/Crouch have extended the effects of his potion if he took smaller sips?

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    Protip: Ignore anything found on HP wiki. (If it's sourced, check up the original source passage and continue to ignore the paraphrased version on HP wiki.)
    – ibid
    Commented Apr 4, 2018 at 8:42
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    This isn't a question that can be answered for regular drugs/meds because it varies from person to person and day to day. If you put magic into the equation ... Btw also note that depending on who makes them potions are more or less effective. And since it's home made, ingredients are not identical always as well
    – Raditz_35
    Commented Apr 4, 2018 at 8:42
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    There must be a minimum dose to be effective after all other wise the vapours escaping from the potion alone would instantly effect people.
    – Ummdustry
    Commented Apr 4, 2018 at 13:01
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    @RichS, not necessarily - that's exactly the sort of reasoning that doesn't always apply to magic. Commented Apr 21, 2018 at 6:21
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    @RichS Not sure it's all that clear. Could be that the effectiveness of the potion depends on having a somewhat specific gravitational relationship to the rest of the universe, which means it needs to have a constant approximate mass. Why would it be that? No idea. Magic.
    – Misha R
    Commented Apr 21, 2018 at 22:25

1 Answer 1


Yes, there is a minimum dosage.

From "Harry Potter and the Deathly Hallows", Chapter Twenty-Five, "Shell Cottage":

There was problem after problem to overcome, not least of which was that their store of Polyjuice Potion was greatly depleted.

'There's really only enough left for one of us,' said Hermione, tilting the thick mud-like Potion against the lamplight.

As for the exact amount required, that isn't made clear in either the movies or the books. The closest there is to any mention of a specific dosage is in Chamber of Secrets (Chapter Twelve) where they each take a "large dollop" of potion.

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