Does reverse osmosis remove all the minerals from water?

It removes most of them. An NSF/ANSI 58 certified RO membrane rejects roughly 90 to 99 percent of total dissolved solids, and that includes calcium, magnesium, sodium, and other dissolved minerals along with the contaminants it is designed to reduce. RO output typically runs 10 to 40 mg/L TDS from source water of 200 to 400 mg/L, so a small fraction of the original mineral content remains rather than literally zero.

Is reverse osmosis water bad for you?

There is no established evidence that drinking RO water harms a healthy person eating a normal diet. The minerals in tap water make up a small share of daily calcium and magnesium intake compared to food. The WHO has published a discussion of low-mineral water that some readers cite as a concern, and it remains debated rather than settled. If you have a medical condition that affects minerals, ask your clinician about your specific situation.

Should I remineralize my RO water?

It is a preference choice, not a health requirement either way. A remineralization stage adds calcium and magnesium back after the membrane, which raises TDS to roughly 50 to 100 mg/L and brings back the mineral taste many people miss. If you find RO water tastes flat, remineralization helps. If you installed RO to cut scale and mineral taste, you may not want it.

Does RO water leach minerals from your body?

This claim circulates online but is not supported by evidence at the levels involved in drinking water. Your body regulates mineral balance through diet and the kidneys, and the amount of calcium or magnesium in tap water is small next to dietary sources. Marketing that frames RO water as draining your body of minerals, or alkaline and remineralized water as a health upgrade, runs ahead of the evidence and has drawn FTC attention.

Where do I actually get most of my minerals?

From food. Dairy, leafy greens, nuts, legumes, and whole grains supply far more calcium and magnesium than drinking water does, even hard water. Water is a minor contributor to total mineral intake for most people on a varied diet. That is the main reason public health bodies do not treat low-mineral drinking water as a general nutritional problem.

Does Reverse Osmosis Remove Minerals? Is RO Water Bad for You?

Health note: this page is educational and is not medical advice. If you have kidney disease, are on dialysis, or have any condition that affects how your body handles minerals, talk to your doctor or dietitian about your water rather than relying on a general guide.

Yes, reverse osmosis removes minerals. That part is not in dispute. An RO membrane has pores small enough to exclude dissolved salts, so calcium and magnesium go down the drain along with the lead, arsenic, PFAS, and nitrate the system is there to reduce. The membrane does not pick and choose. The real question people are asking is the second one in the title, and the honest answer is more measured than either side of the internet wants it to be.

How Much Mineral Does RO Actually Remove

A reverse osmosis membrane certified to NSF/ANSI 58 rejects somewhere around 90 to 99 percent of total dissolved solids. That figure covers calcium, magnesium, sodium, potassium, and the rest of the dissolved load, not just the contaminants.

In practical numbers, if your tap water reads 250 mg/L TDS, RO output usually lands between 10 and 40 mg/L. So the water is not literally mineral-free, but most of what was there is gone. You can watch this happen with a $12 TDS meter, which is also how you tell when the membrane is wearing out.

The minerals that get removed are mostly the same ones that cause hard water: calcium and magnesium. That is why RO water does not leave scale or spotting, and why it tastes thinner than the mineral water some people are used to.

The Mineral Loss in Context

Here is the number that settles most of the worry. The calcium and magnesium in drinking water, even fairly hard water, are a small slice of what you take in over a day. Food does the heavy lifting. Dairy, leafy greens, beans, nuts, and whole grains supply far more of both minerals than a few glasses of tap water ever could.

So when RO strips the minerals from your water, it is removing a minor source, not your main one. For someone eating a varied diet, the difference is unlikely to register nutritionally. That is the same logic the kidney-disease page lays out from the other direction: for patients who need to limit minerals, water is a smaller lever than food, though it can still matter in specific cases.

This is not a reason to be cavalier about it. It is a reason to keep the scale of the effect honest.

What the WHO Actually Said

The document people point to is a World Health Organization chapter titled “Health risks from drinking demineralised water,” by Frantisek Kozisek, published in the WHO volume on nutrients in drinking water (Geneva, 2005). It is real, and it is worth reading rather than quoting secondhand.

What it does: it raises the question of whether water with very low mineral content, the kind produced by demineralization processes including RO and distillation, could matter for people who get a meaningful share of certain minerals from water and little from food. It discusses possible considerations around magnesium and calcium intake in populations where that applies.

What it does not do is declare RO water unsafe for the general public. The findings are debated, much of the underlying research looks at populations and diets different from a typical varied modern diet, and the WHO chapter itself frames the issue as one to consider rather than a settled verdict. Sites selling alkaline ionizers and remineralization gadgets tend to cite the title and skip the nuance. Treat the headline-grabbing version with caution.

The Claim That RO Water Drains Your Body

You will see the argument that low-mineral water is “hungry” and pulls minerals out of your bones or tissues as you drink it. At the trace concentrations involved in normal household drinking water and a varied diet, there is no good evidence this causes clinically meaningful mineral loss in healthy people. (Older WHO-cited studies of distilled water did note increased urinary ion excretion, but those involved very low-mineral water and conditions unlike everyday RO use.) Your body manages mineral balance through diet and the kidneys, and the mineral content of a glass of water is small next to those systems.

The same caution applies in the other direction. Claims that remineralized or alkaline water is healthier, that it changes your body’s pH, or that it delivers some benefit ordinary filtered water does not, run ahead of the evidence. The Federal Trade Commission has scrutinized health marketing around alkaline and ionized water for exactly this reason. We do not make those claims here, and we would be wary of any product that does.

Should You Remineralize RO Water?

This comes down to taste, not health.

RO water at 10 to 40 mg/L tastes flat to a lot of people. The dissolved minerals gave the old water some of its body and character, and stripping them out leaves something thinner. Some people like that clean taste. Others find it oddly empty.

A remineralization stage adds calcium and magnesium bicarbonate back after the membrane. It raises TDS to roughly 50 to 100 mg/L and restores a more familiar taste. The detail on how systems handle this stage is covered in the under-sink RO buying guide.

A few ways to think about the choice:

If you put in RO mainly to cut scale and mineral taste, remineralization works against that goal. Skip it.
If you put in RO for contaminant reduction and just want the water to taste like what you are used to, remineralization is a reasonable add.
If flat taste is the only thing bothering you, a pinch of mineral drops or simply getting used to it are cheaper than a dedicated stage.

None of these is a health decision. It is a preference, and either way is fine.

How RO Compares to Distillation Here

Distillation removes minerals too, and even more thoroughly. Distilled water typically reads near 0 to 2 mg/L TDS, lower than RO output. So everything on this page about low-mineral water applies to distilled water at least as strongly. If the mineral question is what is on your mind, the reverse osmosis versus distillation comparison walks through where each method makes sense for which contaminants.

Test First, Then Decide

The mineral question is downstream of a bigger one: what is actually in your water, and do you need RO at all. Source water varies by region and by well, so test your water before choosing treatment. If your tap is already low in the contaminants RO targets, you may not need a membrane that strips minerals in the first place. If you do have lead, arsenic, nitrate, or PFAS to address, RO earns its place, and the mineral loss is a side effect you can correct for taste if it bothers you.

For a healthy person on a normal diet, drinking RO water is not a known health problem, and remineralization is a taste call rather than a medical one. Where the evidence genuinely hedges, on specific populations and the open questions the WHO raised, the right move is to hedge with it and, if your own health is the concern, to ask your clinician rather than the comment section.