Keto, paleo, carnivore, and low-carb diets can help with weight or blood sugar—but they also shift your body chemistry in ways that quietly raise your kidney stone risk. Not always, not for everyone, but often enough that you should know what’s going on. Especially if you are a past kidney stone sufferer.
What’s happening under the hood
These diets cut sugar—and that’s great. But when the sugar goes down, something else often sneaks up: sodium. Many low-carb, “keto-friendly,” and “sugar-free” foods are packed with salt to make up for lost flavor. Frozen meals, sauces, salad dressings, deli meats, protein bars (get your low-sodium protein bars here), and snacks can all be high in sodium. Most people don’t notice because they’re so focused on cutting carbs.
A high-sodium diet does triple damage for stone formers:
It concentrates your urine.
When you eat a lot of salt, your body tries to get rid of the extra sodium through your kidneys. Sodium pulls water with it—but instead of helping you flush, it actually dehydrates you from the inside out. Your body holds on to water to keep your blood sodium level normal, so you end up peeing less even if you’re drinking plenty.
That’s why so many of my patients say, “Jill, I’m drinking so much but not peeing!”
High sodium keeps water trapped in your tissues and bloodstream instead of letting it pass through as urine. Less urine means your waste products—like calcium and oxalate—become more concentrated, increasing the likelihood they will clump together and form stones.
It robs your bones of calcium.
Sodium and calcium act like magnets—they’re tightly linked inside your body. When you eat too much salt, your blood sodium level rises. Your body can’t let that happen because sodium helps control how much water stays in your blood, which affects your blood pressure and how hard your heart has to work.
To keep sodium in balance, your kidneys remove it from your bloodstream, helping restore normal levels. But calcium sticks to sodium like that little sister who doesn’t let her big sister go out alone. So when your kidneys flush sodium out, calcium gets dragged along for the ride.
That calcium comes from your blood, and your body keeps blood calcium steady by borrowing more calcium from your bones. Over time, that constant “borrowing” can lead to weaker bones. Meanwhile, all that extra calcium your kidneys flush out ends up in your urine, giving kidney stones the perfect building blocks they need.
This sodium-calcium tug-of-war affects more than your kidneys and bones. When sodium levels stay high and your kidneys are working overtime, your body also holds on to more water in the bloodstream. That raises blood pressure and makes your heart pump harder. So too much sodium becomes a triple threat—it stresses your kidneys, weakens your bones, and strains your heart.
This is why, wherever there’s a stone clinic, there’s usually a bone clinic close by. Stones and weak bones often show up together because the same chemistry—too much sodium and calcium loss—is behind both.
It increases the amount of calcium in your urine.
The calcium that leaves your bones doesn’t disappear—it ends up in your urine. So now your urine is concentrated, acidic, and full of calcium. That’s a triple hit your kidneys don’t deserve.
Protein, acid, and the citrate shield
High-protein, low-carb diets load the body with acid. When you eat lots of meat and not enough fruits and veggies, your urine becomes more acidic, and something vital drops: citrate.
Citrate is a natural molecule your body makes that works like a shield—it protects calcium from joining with oxalate and phosphate to form stones.
When your body becomes too acidic, your kidneys retain citrate rather than excreting it in your urine. No citrate means no shield (protection). Once that shield is gone, calcium, oxalate, and phosphate can easily stick together.
Combine that loss of the citrate shield with concentrated urine and extra calcium, and you’ve got the perfect storm for stone formation.
The “healthy” overcorrections
Many people who try to eat better go all-in on “healthy” high-oxalate foods like spinach, almonds, almond flour, almond milk, and chia pudding. These foods are typically eaten in large quantities and every day. That, combined with a lack of calcium in their diet, will cause more oxalate to be absorbed into your bloodstream. Later, it binds to calcium in the urine, forming stones.
Remember: calcium doesn’t cause stones—it helps prevent them by binding oxalate in your gut so it leaves your body safely.
You can still do these diets—just smarter
The good news? You don’t have to quit your favorite plan—you have to balance it.
- Stay hydrated so your urine stays pale.
- Meet your calcium needs with meals to block oxalate.
- Keep sodium between 1,500-2,000 mg/day.
- Add fruits and veggies for natural alkali and more citrate shields.
- Keep meat protein reasonable, not extreme.
Carnivore diet: not for stone formers
A full meat-only plan drives acid sky-high, raises calcium and uric acid in the urine, and removes all plant-based alkali that protects you. If you’ve ever had stones—or want to avoid them—this diet is a hard no.
My specialty: teaching balance
Believe me, I understand your frustration, as I hear it in so many of my one-on-one consults. You change your diet so that you can lower your A1c, reverse heart disease, lose weight, etc, only to end up with an excruciating kidney stone.
You can do keto, paleo, or low-carb and stay stone-free—you need the right guidance. That’s my specialty. In a one-on-one consult, we’ll tailor your plan:
- How much protein is right for you
- Which “healthy” foods to rotate to avoid oxalate overload
- How to meet calcium and hydration goals
- How to lower sodium without losing flavor
- How to read and understand your 24-hour urine test results
- If you love your diet, keep it—make it Kidney Stone Diet® smart.
Book your consult here: https://kidneystonediet.com/work-with-jill/
Action step:
You may have kicked sugar, but salt might still be sneaking in. Start reading your labels, because sodium overload hides in almost every “healthy” low-carb product.
Your friend,
Nurse Jill
P.S. Often people tell me, “I’m eating the Carnivore diet and I haven’t made any stones.” My answer is, “Yet.” Kidney stones don’t come on right away. It takes time. Be careful out there!
The Science behind this article:
https://ajcn.nutrition.org/article/S0002-9165(24)01419-9/fulltext
https://pubmed.ncbi.nlm.nih.gov/12148098
https://pubmed.ncbi.nlm.nih.gov/34070285
https://pubmed.ncbi.nlm.nih.gov/26816783
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