Kidney stones are one of the better-documented risks of long-term ketogenic diets. A 2021 meta-analysis of 36 studies with nearly 2,800 people on keto diets, followed for an average of almost 4 years, found that about 5.9% developed kidney stones: 5.8% of children and 7.9% of adults. Most were uric acid stones or calcium-based stones. Keto can raise the risk because it makes urine more acidic, lowers citrate (which normally helps prevent stones) and, for some people, involves a lot of animal protein and little fluid. Drinking plenty of water, eating plenty of vegetables, not overdoing protein and salt, and getting medical advice if you’ve had stones before all help.
Why keto can raise kidney stone risk
- More acidic urine. Ketosis and high intakes of animal protein make urine more acidic, which favors uric acid stones.
- Less citrate. Citrate in urine binds calcium and helps stop stones forming. Keto diets and acidic urine tend to reduce it.
- Higher uric acid, especially in the first weeks of keto.
- Dehydration. Keto causes the body to lose more water and salt early on, and concentrated urine increases stone risk.
- Lots of animal protein and salt. Diets heavy in meat, bacon, cheese and salty snacks raise calcium and uric acid in urine.
- Fewer fruits and vegetables, which normally provide potassium and citrate.
Who’s most at risk?
- People who’ve had kidney stones before, or have a family history of them.
- People with gout or high uric acid levels. Our guide to the gout diet explains the link.
- People with kidney disease, who shouldn’t start keto without medical advice.
- Children on medical ketogenic diets for epilepsy, who are usually monitored by their medical team and may be given citrate supplements.
- People who don’t drink much water, work in hot conditions or exercise heavily.
Symptoms of kidney stones
Small stones may cause no symptoms, but larger ones can be very painful. The NHS describes kidney stone pain that may come and go, often in the side, back or groin. Other symptoms can include blood in your pee, feeling sick, needing to pee often, and a high temperature or shivering. Get urgent medical help if you have severe pain, a high temperature with pain, or you can’t pee.
How to lower your risk on keto
Drink plenty of fluid
This is the most important step. The NHS advises adults who are prone to kidney stones to drink 2.5 to 3 liters of water a day, and to add fresh lemon juice to water. Pale yellow urine is a good sign you’re drinking enough. Our guide on how much water to drink explains more.
Add lemon or lime
Citrus juice contains citrate. A squeeze of lemon or lime in your water adds very few carbs. Our guide to citrus on keto has the numbers.
Don’t overdo protein
Keto is meant to be moderate in protein, not high. Large amounts of meat increase uric acid and acid load. Our guide to protein on keto explains how much you need.
Eat plenty of low-carb vegetables
Leafy greens, broccoli, zucchini, peppers and avocado provide potassium and alkali, which help balance acidity. Our list of keto vegetables has options.
Watch salt
High salt intake increases calcium in urine. You may need some extra salt in the first weeks of keto to avoid “keto flu,” but the NHS also advises not having too much salt if you’re prone to stones. Get your sodium mostly from cooking and a little broth rather than processed meats and salty snacks.
Get enough calcium from food
It sounds backward, but eating enough calcium helps, because calcium in the gut binds oxalate before it can be absorbed. The NHS advises getting enough calcium in your diet. Don’t take calcium supplements unless your doctor recommends them.
Be careful with high-oxalate foods if you’ve had calcium oxalate stones
Spinach, almonds and other nuts, and rhubarb are high in oxalate. The US National Institute of Diabetes and Digestive and Kidney Diseases says people who’ve had calcium oxalate stones may want to limit high-oxalate foods. Our article on rhubarb and oxalates explains more.
Medical monitoring
If you plan to follow keto for more than a few weeks, it’s sensible to have blood tests, including kidney function and uric acid, before you start and after a few months. Our guide to keto blood tests explains what to ask for. If you’ve had kidney stones before, talk to your doctor before starting; they may recommend a urine test, potassium citrate, or a different diet.
Kidney stone-friendly keto meals
Building meals with these principles in mind keeps keto lower risk:
- Breakfast: Greek yogurt with a few berries and pumpkin seeds, with a large glass of water and lemon.
- Lunch: a big salad of mixed leaves, cucumber, peppers and avocado with chicken or eggs and an olive oil and lemon dressing.
- Dinner: salmon or tofu with roasted zucchini and broccoli, rather than large portions of red meat.
- Snacks: cheese or yogurt, which provide calcium, and vegetable sticks.
- Throughout the day: water spread across the day, aiming for pale urine.
Our Mediterranean keto guide follows a similar pattern, with more vegetables and fish and less red meat.
Common questions
Does keto cause kidney damage?
In people with healthy kidneys, short-term keto isn’t known to damage the kidneys, but kidney stones are a real risk with long-term use. People with existing kidney disease should only follow keto under medical supervision.
Can I prevent stones with supplements?
Some people on medical ketogenic diets are prescribed potassium citrate. Don’t take potassium supplements without medical advice, as too much potassium can be dangerous.
Should I stop keto if I get a kidney stone?
Talk to your doctor. They’ll look at the type of stone and your overall health before advising whether to change your diet.
Safety note: Keto isn’t suitable for everyone. If you have diabetes, kidney or liver disease, take regular medication, or are pregnant or breastfeeding, talk to your doctor before cutting carbs this far (why it matters).
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
