No. Distilled water is not toxic, is sold as a drinking water product, and does nothing dangerous to a person drinking it in normal amounts. The claim circulates widely enough to be worth answering properly, because the reasoning behind it sounds plausible and is a misapplication of something that is genuinely true in a different context.
Where the claim comes from
Distilled water is a solvent with nothing dissolved in it, and in industrial and laboratory contexts that makes it aggressive: it readily takes up carbon dioxide from air, and it corrodes some metals that ordinary water leaves alone. That is a real property. The leap made in the popular version is that the same aggressiveness strips minerals out of a person. It does not, because the water stops being mineral free the instant it meets saliva and stomach contents.
Why the biology does not work that way
The stomach is strongly acidic and full of dissolved salts, so any water arriving there is immediately loaded with ions regardless of what it contained beforehand. Absorption in the intestine is identical. The kidneys regulate electrolyte balance against total intake, which food dominates by a wide margin. There is no mechanism by which drinking a glass of mineral free water leaches calcium out of bone or sodium out of blood, and no evidence of that happening.
The risk that is real
Water intoxication, and it has nothing to do with distillation. Drinking a very large volume of any water in a short period can dilute blood sodium to a dangerous level, and that has caused deaths in endurance events and in drinking contests. Filtered, mineral, spring and distilled water all carry it equally, because the factor is volume rather than composition. Replacing electrolytes matters for anyone drinking heavily in heat or during prolonged exertion, whatever their water source.
The reasonable version of the concern
Where distilled water is a household's sole supply for a long period, and diet is poor, the absence of any mineral contribution is worth addressing, and remineralizing is the straightforward answer. It also improves the taste, which is the objection most people actually have. The USGS classes water as soft at 0 to 60 mg/L as calcium carbonate through to very hard above 180, so what you forgo depends entirely on what you were drinking before. Our drinking water guide covers remineralizing options.
Questions people ask about can distilled water kill you
Is distilled water dangerous to drink?
No. It is sold as a drinking water product and does nothing harmful in normal amounts. The claim is a misapplied industrial fact.
Does it leach minerals out of your body?
No. It stops being mineral free the moment it meets saliva and stomach contents, and absorption proceeds identically to any water.
So is there any real water risk?
Water intoxication from drinking a very large volume quickly, which applies equally to every kind of water. Volume is the factor, not purity.
Should I remineralize it?
Worth doing if it is your sole supply long term, and worth doing anyway for the taste, which is the real objection most people have.