Kidney Stone Prevention: How Much Water Should You Drink?
By: Houston Methodist The Woodlands Hospital | Published 01/29/2023
Recent estimates suggest that 1 in 11 Americans will experience kidney stones in their lifetime, so it goes without saying that we should all take kidney stone prevention seriously.
"It's a very prevalent disease," says Dr. Monica Morgan, a urologist at Houston Methodist. "Kidney stone recurrence is common as well. A person who's had a stone in the past has a 50% chance of getting another one if they don't take the necessary steps to prevent them."
What can you do to stay stone-free? Maybe you've heard that simply drinking enough water is all it takes.
Can dehydration cause kidney stones?
"Absolutely," says Dr. Morgan. "There's a lot of data showing that urine volume is incredibly important for stone prevention."
Kidney stones form when minerals and salts in the urine combine to create hard deposits inside the kidney. For instance, calcium stones — the most common type of kidney stone — are typically composed of calcium and oxalate that has attached and lodged in kidney tissue.
The odds of this happening increase if you're not drinking enough water. As your urine volume decreases, these minerals become more concentrated — making their chances of interacting more likely.
"It's why low fluid intake is a huge kidney stone risk factor," explains Dr. Morgan. "This risk increases even further if you also have too much of one of these minerals in your urine for one reason or another. Hypercalciuria, high urine calcium, is one example of this."
Fortunately, adequate hydration can help counteract this, Dr. Morgan notes. It's one of the most important ways of preventing kidney stones, in fact.
"The more water you drink, the more diluted your urine will be," says Dr. Morgan. "This means that the concentration of calcium and other minerals in your urine will be less, reducing the chance of stone formation."
How much water does it take to prevent kidney stones? It can depend.
For most people, prevention starts by following general recommendations for adequate hydration. (Related: How Much Water Should You Drink In a Day?)
But for those who've passed one of these painful stones before, hydration becomes an even bigger priority.
Do people prone to kidney stones need more water?
While some people may be able to get away with drinking just a liter of water (or less) per day, Dr. Morgan points out that those with a previous history of kidney stones have a greater burden of increasing their fluid intake.
"We want kidney stone formers to drink enough water to produce 2.5 to 3 liters of urine per day," says Dr. Morgan. "But because your body uses some of the water you drink for necessary processes, like digestion, and you lose water through sweat, urine volume isn't identical to fluid intake."
Given this, Dr. Morgan says people prone to kidney stones should, ideally, drink more than 3 liters per day — that is, at least 13 8-ounce glasses. However, the exact amount depends on the person's body weight and many other factors.
"Clinical studies set this number as the goal, but we know it can be somewhat unrealistic for many people," says Dr. Morgan. "If you give people unreasonable goals, they're unlikely to meet them, so my practical recommendation for preventing stone recurrence falls somewhere between getting 2.5 to 3 liters of water per day."
If this is a big shift for you, start slow — adding more and more water to your daily fluid intake gradually.
"Yes, the goal is 2.5 to 3 liters or more, but usually any additionally amount of water is better than what you were drinking in the past," says Dr. Morgan.
You'll also want to spread out the water you drink during the day, rather than chugging it all at once.
What kind of water is best for kidney stones?
You might wonder whether there's a "best" type of water for kidney stone prevention. Alkaline water, a popular Internet remedy, is often touted.
"There's no scientific data to prove that one type of water is better than another at preventing kidney stones," says Dr. Morgan. "Some studies do show that magnesium and bicarbonate are good to have in water, but there's no hard data to prove that alkaline water is actually better at this point in time."
On the other hand, some studies show that hard water (most tap water in the U.S.) could potentially increase the risk of kidney stones due to its high mineral content. But the evidence is sparse.
"Compliance is more important than the type of water, so we really just want people actually drinking water — regardless of type," adds Dr. Morgan. "The key to preventing kidney stone formation really is to increase and maintain an adequate urine volume."
Do soft drinks cause kidney stones?
You might think a can of soda counts toward the fluid intake needed to prevent kidney stone recurrence. It's fluid, after all. But watch out.
"Dark sodas, like cola and root beer, have actually been shown to increase the risk of kidney stones," warns Dr. Morgan. "If you're drinking these types of sodas because you're trying to increase your urine volume but don't like the taste of plain water, there are all kinds of tricks you can use to get more fluids."
To increase your fluid intake without just drinking more soda, try:
- Switching to sparkling water
- Drinking artificially sweetened fruit drinks, like diet lemonade or diet limeade
- Adding a squeeze of lime or lemon to your water
- Eating hydrating foods, like lettuce, cucumber, celery, tomatoes, bell peppers, skim milk, yogurt, broths and soups
You might also try motivating yourself to drink plain old water by getting an app to track how much you're drinking or buying a water bottle and carrying it around with you whenever you can.
"Try anything that can help make water a priority," adds Dr. Morgan. "People may brush off kidney stones or can forget the pain they went through in the emergency room. However, stones are painful, inconvenient, can cause kidney damage and increase the burden on our healthcare system. Hydration really is one of the primary ways to prevent them."
By: Katie McCallum