Distilled water is drinkable and there is no safety reason to avoid it. Over a longer period two practical issues come up that the usual mineral debate never mentions, and both are about what happens to the water after it leaves the still rather than about the water itself.
The direct answer
Distillation boils water and condenses the vapour, leaving dissolved solids, metals and organisms behind, so what is collected is water with very little in it. Drinking it is not harmful. The objection usually raised, that it deprives you of dietary calcium and magnesium, is modest in proportion: the USGS describes hardness as exactly those two minerals, and for someone eating normally food supplies the great majority of both while water contributes a small share.
Caveat one: it has no residual and picks things up
Distilled water carries no disinfectant, so once it is in a jug or a bottle nothing suppresses growth. Stored in a warm kitchen in an open container it deteriorates like any other treated water. Keep it in clean covered containers, refrigerate what is not used soon, and do not top up an old container with fresh water, which perpetuates whatever established itself in the first batch. This applies to filtered and reverse osmosis water equally.
Caveat two: it is chemically aggressive
Water with almost nothing dissolved in it is a good solvent, so it takes up what it touches more readily than ordinary water does. That matters mainly for storage and plumbing rather than health: keep it in containers intended for drinking water rather than reusing food containers or unmarked plastics, and be aware that this is why whole house systems producing demineralized water include remineralization or blending before it enters the pipework.
The practical alternative
For everyday drinking, buying distilled water is expensive and carrying it is tedious, and a home distiller is slow, uses a meaningful amount of electricity and needs descaling. Reverse osmosis with a remineralization cartridge gives a comparable reduction, produces on demand, tastes like water rather than flat, and costs less over a year. Distilled water remains the right choice for steam irons, humidifiers and similar appliances. Our softener guide covers the hardness question across the house.
Questions people ask about is distilled water drinkable
Can I drink distilled water every day?
Yes. It is safe; the usual objections concern taste and mineral content, both modest for someone eating normally.
Does it keep well once opened?
No better than any treated water. It has no disinfectant residual, so store it covered and refrigerated and use it reasonably soon.
Why is it described as aggressive?
Water with almost nothing dissolved is a good solvent, so it takes up what it contacts more readily. That matters for containers and plumbing.
Is there a cheaper everyday option?
Reverse osmosis with a remineralization cartridge: comparable reduction, produced on demand, and it tastes like water.