Distilled water is safe to drink, so the more useful question is whether it is good for the purpose you have in mind. In practice the answer splits: for a few specific uses it is the recommended water and nothing else will do, and for everyday household drinking it is an expensive way to get something a tap filter delivers better.
Where it is genuinely the right choice
Appliances where mineral deposits cause damage or nuisance: steam irons, humidifiers, CPAP machines, steam cleaners and similar. Car batteries and some cooling systems specify it. Laboratory and some medical uses require it. In every one of those the point is the absence of dissolved minerals, and using tap water instead leaves scale, mineral dust or contamination that the equipment was not designed to tolerate. This is where households usually encounter it and where buying it makes obvious sense.
Why it is unrewarding to drink
The USGS describes hardness as dissolved calcium and magnesium, and those, with bicarbonates and a little sodium, are much of what gives water its taste. Distillation removes essentially all of it, so what is left tastes flat, and that is more noticeable when it is all you drink and in tea and coffee where mineral content affects extraction. There is nothing unsafe about it; it is simply not enjoyable, which is why households that try it usually do not persist.
The mineral intake argument
The objection raised is that water with no minerals removes a dietary source of calcium and magnesium. For someone eating normally, food supplies the great majority of both and water a small share, so this is not a route to deficiency. It carries more weight where a diet is already low in those minerals, and it is the reason remineralization stages are fitted to reverse osmosis systems: the same broad reduction with a small mineral content put back, which tastes like water again.
What to do instead for everyday drinking
If the reason for considering distilled water is distrust of the tap supply, treat the supply. Find out what is actually in it, then fit the stage that addresses it: carbon for chlorine and taste, reverse osmosis with remineralization for a broad reduction that still tastes right, a softener if the complaint is scale. All of those cost less over a year than buying distilled water and produce on demand. Our drinking water filter guide covers the options by format.
Questions people ask about is distilled water good for drinking
Is distilled water safe to drink?
Yes. It is water with the dissolved material removed. The objections are taste and mineral content rather than safety.
What is it actually recommended for?
Steam irons, humidifiers, CPAP machines, steam cleaners, car batteries and laboratory use, where mineral deposits cause problems.
Why does it taste flat?
Dissolved minerals give water its taste and distillation removes essentially all of them.
Is there a better everyday option?
Reverse osmosis with a remineralization stage: a similar broad reduction with enough mineral put back to taste like water.