Last updated: · By Emma Collins
If you follow a ketogenic diet, it can raise your risk of kidney stones, and the risk is not the same for everyone. A pooled analysis of published studies estimated that about 5.9% of people on keto diets developed kidney stones, with the rate around 7.9% in adults and 5.8% in children. Most people on keto do not form stones, but the risk is real enough that you should know the warning signs, understand your personal risk factors, and talk with a doctor before you start or continue the diet.
This guide explains how stones form, why a ketogenic diet may increase the risk, what the research does and does not show, and the prevention steps with the best evidence behind them. It is general information, not medical advice. If you have a history of stones, kidney disease, gout, or a condition that affects your urine, get individual guidance before making major diet changes.
Key Takeaways
- A pooled analysis of published studies estimated that about 5.9% of people on keto diets developed kidney stones, with about 7.9% in adults and 5.8% in children.
- Most people on keto do not form stones, but the risk is real, so know the warning signs and talk with a doctor before starting or continuing the diet.
- Keto may raise urinary calcium, lower urinary citrate, and make urine more acidic, and low fluid intake can make these effects worse.
- According to the NIDDK, drinking enough fluid each day is the most effective prevention for most types of kidney stones.
- Many keto favorites such as spinach, almonds, and cashews are high in oxalate, so people with a stone history should limit them and talk with a doctor or dietitian.
What Kidney Stones Are and Why They Form
Kidney stones are hard deposits that form in the kidneys and can travel into the urinary tract. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), stones form when calcium, oxalate, and phosphorus reach high levels in the urine, even though these minerals are normally present at safe levels. Urine that is concentrated, meaning there is less water to dilute these minerals, makes stone formation more likely.
Symptoms often include severe pain in the back or side, pain that moves toward the groin, blood in the urine, nausea, and a frequent or urgent need to urinate. Some stones pass without much trouble, while others cause significant pain or block urine flow. If you have fever or chills along with side pain, or you cannot urinate, seek medical care right away, because these can signal infection or a blockage.
Common Stone Types
Calcium oxalate is the most common type of kidney stone in the general population. Uric acid stones are less common overall, but they are the type most often reported in people on ketogenic diets, according to the meta-analysis discussed below. Uric acid stones tend to form when urine stays persistently acidic, which is one reason diet can matter.
The Ketogenic Diet in Brief
The ketogenic diet is a very low-carbohydrate, high-fat eating pattern. It is often described as roughly 70 to 80% of calories from fat, 5 to 10% from carbohydrates, and 10 to 20% from protein, though exact targets vary by program. By sharply limiting carbohydrates, the diet shifts the body toward burning fat and producing ketones, a state called ketosis.
Common keto foods include meats, fish, eggs, butter, olive oil, avocados, cheese, and non-starchy vegetables. Grains, sugar, most fruits, and many legumes are restricted. Short-term studies show benefits for weight loss and blood sugar control in some people, but long-term effects are still being studied. Restrictive eating can also lead to nutrient gaps if the diet is not planned carefully.
Kidney Stones and Keto Diet: What the Evidence Shows
The strongest evidence linking keto and kidney stones comes from studies in children, many of whom were following the diet to treat seizure disorders. A Johns Hopkins case-control study, published in the medical literature and indexed on PubMed, compared children on a ketogenic diet who developed stones with those who stayed stone-free. The study found kidney stones were linked to ketogenic diet use in children with refractory seizure disorders.
A later systematic review and meta-analysis pulled together 36 studies including 2,795 patients. It estimated kidney stone incidence on ketogenic diets at about 5.9% overall, roughly 7.9% in adults and 5.8% in children, and found uric acid stones to be the most common type. You can review the analysis in the review indexed by UT Health San Antonio Scholars.
| Population on ketogenic diet | Estimated kidney stone incidence | What to keep in mind |
|---|---|---|
| All patients pooled | About 5.9% | Pooled estimate across 36 studies and 2,795 patients |
| Adults | About 7.9% | Fewer adult studies; many adults in keto research have other conditions |
| Children | About 5.8% | Many children were on keto for seizure control, under medical supervision |
Limits of the Research
These numbers are useful, but they come with important caveats. Studies differed in design, how stones were detected, how long people followed the diet, and why they were on it. Many were small, and some were observational, which means they can show an association but cannot prove the diet directly caused the stones. Stone risk can also depend on factors these studies did not measure, such as genetics, fluid intake, and existing metabolic conditions.
Because most data come from clinical populations, the results may not translate neatly to a healthy adult doing keto for weight loss. That does not mean the risk is zero. It means your personal risk is better estimated with your medical history and, when appropriate, urine and blood tests than with a single average number.
Why Keto May Raise Stone Risk
Researchers have proposed several mechanisms, though not all have been proven in people on keto. One is that the diet may increase how much calcium the kidneys send into the urine. Another is that it may lower urinary citrate. Citrate is a natural substance that helps block calcium from forming crystals, so lower levels may leave more room for stones to form.
Diets that are high in animal protein and very low in carbohydrates can also make urine more acidic. Acidic urine is a known factor in uric acid stone formation. Low fluid intake makes the problem worse, because less water means more concentrated urine, and many people on keto do not realize they are drinking less than they need.
- Increased urinary calcium excretion, a proposed mechanism
- Lower urinary citrate, which normally helps prevent crystal formation
- More acidic urine, which favors uric acid stones
- Concentrated urine from insufficient fluid intake
- High intake of some oxalate-rich foods, which can raise urinary oxalate
Risk Factors That Raise Your Chances
Keto itself is one risk factor, but it is rarely the only one. Your overall risk depends on your health history, how much you drink, what else you eat, and how long you stay on the diet. The factors below are the ones most often linked to stones in the research and in clinical guidance.
Personal and Medical History
If you have had kidney stones before, your risk is higher, and you should be especially careful. Other conditions linked to stone formation include gout, inflammatory bowel disease, certain metabolic disorders, and high calcium levels in the urine, called hypercalciuria. Some medications also affect stone risk, so review your full medication list with your doctor.
Diet and Fluid Habits
Low fluid intake is one of the most common and most fixable risk factors. Heavy reliance on animal protein, high sodium intake, and high oxalate foods can also add to the risk. Very low dietary calcium may seem helpful, but it can actually raise oxalate absorption, so cutting calcium is not a good strategy.
- Personal history of kidney stones
- Dehydration or drinking less water than you need
- Gout, inflammatory bowel disease, or other metabolic conditions
- Family history of kidney stones
- Hypercalciuria or abnormal urine test results
- Long-term high intake of oxalate-rich foods without monitoring
Prevention: Hydration Comes First
The NIDDK notes that for most types of kidney stones, drinking enough fluid each day is the most effective prevention. Fluid keeps urine diluted and helps flush out the minerals that form stones. For people on a ketogenic diet, this is the single most important habit to build.
How Much Fluid Do You Need?
The right amount depends on your body size, activity, climate, sweat loss, and kidney health, so there is no single number that fits everyone. Your clinician may set a target for how much urine you should produce each day, which is a more useful guide than a fixed water count. If you have heart, kidney, or fluid-balance conditions, ask before increasing fluids significantly.
A practical check is urine color. Pale, light-yellow urine usually means you are drinking enough, while dark yellow urine suggests you need more fluid. Spread your intake across the day rather than drinking a large amount all at once.
A Practical Hydration Plan
- Ask your doctor what daily fluid or urine output target fits your health history.
- Carry a water bottle and sip steadily through the day, especially during exercise or hot weather.
- Check your urine color each morning and midday as a rough guide.
- Limit sugary drinks, and watch caffeine and alcohol, which can increase fluid loss.
- Get your urine and blood tests as recommended, and adjust your plan with your clinician.
Managing Oxalate and Food Choices
Oxalate is a compound found naturally in many plant foods. When oxalate combines with calcium in the urine, it can form calcium oxalate stones. Many keto favorites, including some nuts and leafy greens, are high in oxalate, so keto eaters need to pay attention to this detail.
| Food group | Examples | Suggested approach |
|---|---|---|
| High oxalate | Spinach, rhubarb, beets, almonds, cashews, chocolate, and some teas | Limit portions, especially if you have a stone history; ask your doctor or a dietitian about targets |
| Moderate oxalate | Some nuts such as macadamias, some vegetables, and some berries | Keep portions moderate and vary your choices |
| Lower oxalate | Cauliflower, cabbage, zucchini, cucumber, eggs, and most meats | Good keto staples that are typically lower in oxalate |
Dietary calcium eaten with meals is generally helpful because it binds oxalate in the gut and reduces how much is absorbed. Calcium supplements taken without food are a different situation, so ask your clinician before adding them. Likewise, reducing animal protein may help some people, but cutting it drastically can lead to other problems, so balance is key.
Potassium Citrate: What the Evidence Says
Potassium citrate is a prescription medication that raises urinary citrate and makes urine less acidic. It is used to prevent certain types of kidney stones, and it has been studied in children who were following ketogenic diets. In those studies, potassium citrate was associated with fewer stones, which is one reason it has drawn attention in keto research.
The evidence has limits. Much of the data comes from pediatric studies in clinical settings, and the research in adults on keto diets is less complete. Potassium citrate can cause side effects, including stomach upset, and it can raise potassium levels to unsafe levels in people with kidney disease or those taking certain medications. You should never start it on your own. If your doctor recommends it, the decision should be based on your urine tests, medical history, and kidney function.
When to See a Doctor
Talk with your doctor before starting keto if you have a history of kidney stones, kidney disease, gout, or a condition that affects your urine or electrolytes. Your clinician may check kidney function, blood calcium, uric acid, and urine chemistry to understand your risk. For people with existing kidney disease, the picture is more complicated, and the right choice may differ.
Seek care promptly if you have severe side or back pain, blood in the urine, fever with pain, or trouble urinating. These symptoms need medical evaluation, and in some cases they require urgent treatment.
Related Reading on Keto and Kidneys
If you already have kidney problems, it is important to understand the broader risks. Our guide on what doctors warn about when keto is combined with kidney disease covers the specific concerns clinicians raise. If you are weighing whether the diet could ever be appropriate in that setting, read our overview of when keto for kidney disease may or may not make sense.
Frequently Asked Questions
Can a keto diet cause kidney stones?
A keto diet can increase the risk of kidney stones, based on studies that found stones in a meaningful share of people on the diet. The mechanisms are not fully proven, but they likely involve changes in urine calcium, citrate, and acidity, along with fluid intake. Most people on keto do not develop stones, but it is wise to know the warning signs.
How common are kidney stones on keto?
A pooled analysis of 36 studies estimated about 5.9% of people on ketogenic diets developed kidney stones, with about 7.9% in adults and 5.8% in children. These figures come from varied study designs and populations, so your personal risk may be higher or lower. Your history and test results matter more than the average.
Does potassium citrate prevent kidney stones on keto?
Potassium citrate has been associated with fewer kidney stones in children on ketogenic diets, which is why researchers have studied it. The evidence in adults is less clear. It is a prescription medication with possible side effects, so use it only if your doctor recommends it after reviewing your urine and kidney tests.
How much water should I drink on keto?
No single amount fits everyone, because needs vary with body size, activity, climate, and health conditions. A useful goal is steady intake that keeps urine pale or light yellow, and your clinician may set a specific urine output target. If you have heart, kidney, or fluid-balance problems, check with your doctor before increasing your fluids.
Are spinach and nuts bad on keto?
They are not off-limits for everyone, but spinach, almonds, cashews, and other high-oxalate foods can raise urinary oxalate. If you have a history of calcium oxalate stones, it makes sense to limit them and eat them in moderate portions. A dietitian can help you build a keto plan that is lower in oxalate without losing key nutrients.
Conclusion
Kidney stones and keto diet risk are connected, but the risk is manageable for most people who understand it. The keto diet may raise urinary calcium, lower citrate, and make urine more acidic, and low fluid intake can make all of this worse. Staying well hydrated, watching oxalate-rich foods, and getting medical guidance are the most practical steps you can take.
Before starting or continuing a ketogenic diet, talk with your doctor, especially if you have a history of stones or kidney disease. Your clinician can help you weigh the benefits and risks based on your own health, not on averages alone.
This article is for informational purposes only and is not medical advice. Talk to your doctor or a registered dietitian before changing your diet, especially if you have a medical condition or take medication. Read our medical disclaimer and editorial policy.
