Welcome to Ask The Doctor.
This all depends on the quantity of Ectasy (NDMA) you have consumed and the sensitivity of the test that your laboratory would be using. Also it depends on what is the potency of NDMA.
However, it's half life is 7 hours but small amount of it can persist in the body for long.
If you have taking heavy amount for long, this can persist in the body as cumulative dose and can be shown up in the tests.
I hope it helps.
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