Avoid the Big Oxalates, Don't Sweat the Small Ones
Calcium oxalate stones make up about 75% of all kidney stones. The good news: most of the foods that raise your risk are foods you don't have to give up entirely — you just need to know which ones matter most.
There are different types of kidney stones, but the largest and by far the most common are calcium oxalate stones. They form when there's too much oxalate in the urine, which binds to calcium and crystallizes over time. Unlike uric acid stones, which can sometimes be dissolved, calcium oxalate stones can't — so if you've had one before, prevention really is the only strategy that works. And since a first stone often means a real chance of a second, knowing which foods actually drive your oxalate levels up is one of the most effective things you can do.
What Foods Contain Oxalates?
Oxalate shows up in a surprising number of foods, and unfortunately, some of the biggest offenders are otherwise some of the healthiest things you can eat. Spinach, kale, beets, okra, and certain nuts all sit near the top of the list. That's exactly why hydration matters so much — and never more than right after eating something oxalate-heavy, when flushing your kidneys with water does the most work.
| Oxalate Level | Examples |
|---|---|
| Highest (limit these) | Beets, spinach, kale, okra, some nuts, dark chocolate, tea |
| Moderate | Blueberries, celery, and other foods that get labeled "high" but aren't close to the worst offenders |
| Lower (normal consumption is fine) | Bananas, apples, grapes, watermelon, potatoes, and many other vegetables |
Should I Worry About All the Foods on the List?
You'll often hear a food described as "high in oxalates" without any real context, and that label alone can be misleading. Beets, for example, contain roughly 75 times more oxalate than foods that also carry the "high" label, like blueberries and celery. Bananas, apples, grapes, watermelon, potatoes, and most other vegetables fall in the bottom half of the list, and normal consumption of those is generally fine.
A simple trick: boiling vegetables can cut their oxalate content by roughly 50%. If you do eat something from the top half of the list, boil it when you can, keep the portion reasonable, and follow it up with plenty of water — ideally with electrolytes like KSPtabs, so you're flushing your kidneys, getting citrate's protective effect, and giving the magnesium and B6 a chance to help keep oxalate levels in check, all at the same time.
How Do I Know What Kind of Kidney Stones I Make?
Knowing your stone type matters for prevention, since not all stones form for the same reason. If you don't already know what kind you make, ask your doctor — and if they can't tell you, request a 24-hour urine test. It's the single best way to understand why you're forming stones in the first place, so your prevention plan actually targets the right thing.
Completing one of these collections is nobody's idea of fun, especially after going through something as painful as a kidney stone. But between the inconvenience of a urine collection and the pain of another stone, it's not a close call — it's worth doing.
Why Hydration Still Matters Most
Managing oxalate-heavy foods only helps if your kidneys can actually flush what you're taking in. Oxalate becomes a problem when it's concentrated in the urine — the less diluted your urine is, the more chances oxalate and calcium have to bond and crystallize. That's why doctors consistently recommend higher water intake for anyone with a history of kidney stones, regardless of stone type.
That said, hydration alone isn't a complete fix. A large 2026 clinical trial (the PUSH trial, published in The Lancet) randomized over 1,600 stone formers to an intensive hydration coaching program versus usual care — and despite meaningfully higher urine output in the hydration group, it didn't significantly reduce stone recurrence on its own. The takeaway isn't that hydration doesn't matter; it's that water alone is rarely enough. Pairing hydration with something that actively changes your urine chemistry — like citrate — is what makes the difference. It also matters whether your body actually holds onto the water you drink in the first place, which is where balanced sodium and potassium come in — without them, a lot of what you drink passes through before it can do much good.
How KSPtabs Helps Protect Your Kidneys
KSPtabs was developed by a board-certified urologist specifically to help counteract this problem. Add it to your water and the citrate goes to work right away, binding to calcium before oxalate gets the chance to — meaning less free calcium in your urine and fewer opportunities for calcium oxalate crystals to form in the first place. But citrate isn't the only thing doing the work: KSPtabs also delivers balanced sodium and potassium to help your body actually hold onto the water you drink, plus magnesium and vitamin B6, which help keep oxalate levels in check from the start.
| What's in KSPtabs | What It Does |
|---|---|
| Citrate | Binds to calcium in your urine before oxalate can, so fewer crystals get the chance to form |
| Magnesium | Works alongside citrate and may help lower how much oxalate ends up in your urine in the first place |
| Vitamin B6 | Supports your body's natural process for handling oxalate, so less of it ends up somewhere it can cause problems |
| Balanced Sodium | Helps your body actually hold onto the water you drink, without the harsh "ocean water" taste of high-sodium drinks |
| Potassium | Works alongside sodium to keep your fluids balanced and support proper hydration |
The goal isn't to swear off spinach and beets forever. It's to keep enjoying the foods you like while giving your kidneys the backup they need to handle them.
Frequently Asked Questions
Can I still eat spinach or kale if I've had a kidney stone?
In most cases, yes — in reasonable portions. Boiling cuts oxalate content by roughly half, and pairing these foods with a calcium source (like dairy) at the same meal helps bind oxalate in the gut before it ever reaches your kidneys. This is also where KSPtabs can help: the citrate binds to calcium in your urine before oxalate gets the chance to, giving you an extra layer of protection alongside boiling and staying hydrated.
Do I need to avoid oxalates completely?
Almost never. Complete oxalate avoidance is really only recommended for a small subset of people with a specific diagnosis (hyperoxaluria) under a doctor's care. For most stone formers, the more realistic strategy is limiting the highest-oxalate foods, staying hydrated, and giving your body extra backup — like the citrate in KSPtabs — rather than eliminating oxalate altogether.
Does eating calcium with oxalate-rich foods actually help?
Yes. Calcium and oxalate bind to each other in the digestive tract when eaten together, which means less free oxalate is available to be absorbed and later concentrated in the urine. The key is eating them in the same meal — taking a calcium supplement at a completely different time of day doesn't have the same effect. KSPtabs works on the other end of that same process: instead of binding oxalate in your gut, its citrate binds to calcium in your urine, covering the oxalate that does make it through.
How much water should I actually be drinking?
Needs vary by person, activity level, and climate, so this is really a conversation for your doctor or urologist. A commonly cited general target for stone formers is enough fluid to produce close to 2.5 liters of urine a day — pale yellow urine is usually a good sign you're close. Adding KSPtabs to your water is an easy way to make that daily habit do more work: the sodium and potassium help your body actually retain what you drink instead of it passing straight through, while you're also getting the citrate benefit at the same time.
Want to try it out? The Trial Pack is the easiest place to start — all three flavors, so you can find your favorite before ordering a month supply or subscription.
This article is for general informational purposes and is not a substitute for medical advice. Talk to your doctor about your specific kidney stone risk and diet.
