Top 8 Reasons You Keep Getting Kidney Stones On A Low Oxalate Diet

You’ve been diligently following a low oxalate diet and you keep getting stones. How can this be? It is a terrible place to be in: thinking you are doing everything “right” and still getting stone after stone. There must be more to the puzzle.

Low oxalate diets are not necessarily the most effective way to prevent kidney stones. Healthy eating for kidney stones is about a lot more than oxalate. In fact, I don’t even give many of my patients an oxalate food list! Healthy eating for stone prevention must be based on your individual urine risk factors. A low oxalate diet is only necessary if one of your risk factors is high urine oxalate.

Here are the most common mistakes I see people make with low oxalate diets.

1. You Don’t Have Oxalate Kidney Stones

This happens all the time. Unfortunately, people are often told to follow a low oxalate diet without even knowing what kind of kidney stones they have. About 80% of kidney stones are calcium oxalate, so sometimes doctors assume kidney stones are calcium oxalate. However, there are many different kinds of kidney stones including phosphate, uric acid, struvite and cystine. A study found that emergency rooms often given inappropriate nutrition advice for kidney stones. (1)

If you do not have oxalate kidney stones, following a low oxalate diet is not going to prevent more kidney stones.

2. You Don’t Have High Urine Oxalate

Even people who have oxalate kidney stones do not necessarily need to follow a low oxalate diet. Oxalate kidney stones can be caused by a variety of things. In fact, high urine calcium is the most common cause of oxalate kidney stones, not high urine oxalate. (1) Urine citrate, pH and other factors also play a role.

If you don’t have high levels of oxalate in your urine, cutting back how much oxalate you eat isn’t going to make much difference. Only a 24-hour urine test will be able to tell you and your doctor if you have high urine oxalate.

More about who needs a low oxalate diet in the first place!

3. You Aren’t Drinking Enough Water

Drinking enough water is the most important part of kidney stone prevention. (1) No matter how healthy your diet is, if you are not drinking enough water, you may be at risk for kidney stones.

The American Urological Association recommends drinking enough fluid to make 2 1/2 liters of urine per day. (2) For most people, this means about 3 liters of fluid per day. Your goal might be more or less depending on your medical history and lifestyle factors. Ask your doctor or dietitian how much water is right for you.

Getting in this much water is no easy task! Many of my patients have found that using a smart water bottle, like the Hidrate Spark* to be incredibly helpful to meet their fluid goals!

HidrateSpark 3 -- The World's Smartest Water Bottle

4. You Aren’t Eating Enough Fruits & Vegetables

Some people overdo the oxalate restriction and cut out too many fruits and vegetables. Contradictory oxalate food lists and websites spreading false, alarmist information about oxalate can scare people away from eating ANY healthy fruits and veggies. However, fruits and vegetables are non-negotiable for kidney stone prevention.

In every single study I’ve ever read, people who eat more fruits and vegetables are less likely to form kidney stones. (3) Although most fruits and vegetables do have a least a little oxalate, they also have all sorts of good things in them that can help prevent kidney stones. Citrate, potassium, magnesium and alkali are examples.(1) They are also a critical piece of a balanced meal. Without them, meals are usually too high in either protein or carbohydrate, which could contribute to stones as well.

A strict low oxalate diet of 50mg or less per day makes it very difficult to eat a variety of nutritious foods. And, may be doing more harm than good. For most people, simply avoiding foods very high in oxalate, along with eating enough calcium, is enough to bring urine oxalate down to safe levels.

Foods Very High in Oxalate

  • Spinach
  • Almonds & almond products
  • Beets
  • Rhubarb
  • Raspberries
  • Navy Beans
  • Miso

If taking these foods out of your diet doesn’t lower urine oxalate, I usually recommend 100mg of oxalate per day. However, your diet should be individualized to your 24-hour urine results.

5. You Aren’t Eating Enough Calcium

In a landmark study, people who ate enough calcium had a 50% reduced risk of kidney stones compared to people who limited calcium – both groups were following a low oxalate diet. (4)

Calcium is so important because it binds to oxalate in the intestine and reduces oxalate absorption. Eating enough calcium is a very effective way to reduce urine oxalate.

More about calcium and kidney stones.

6. You Aren’t Paying Attention To What You DO Eat

Healthy eating is never about just staying away from one nutrient. It is always more important to pay attention to what you ARE eating.

Oxalate is only one (possible) piece of kidney stone nutrition. Eating too much protein, sodium and added sugar can all play a role too. (3)

Learn more about healthy eating for calcium oxalate kidney stone prevention.

7. You Are Taking Vitamin C Supplements

Oxalate in your food is only one source of oxalate in the body. Your liver can make oxalate from certain things including some proteins, fructose and vitamin C. Vitamin C is a big one. In fact, a study found that vitamin C was the biggest contributor to oxalate in urine! (4)

If you have high urine oxalate, stay away from all types of vitamin C supplements. Yes, cough drops included! Vitamin C that occurs naturally in food is not a concern. People who eat lots of fruit are less likely to have kidney stones.

8. Kidney Stones Weren’t Caused By Your Diet

Lastly, it is important to acknowledge the limitations of nutrition. Not all kidney stones are caused by what you eat. If diet is not the cause, changing it isn’t going to help prevent kidney stones. It is important to find a doctor who specializes in kidney stone prevention to figure out the cause of your kidney stones and determine if eating (or avoiding!) certain foods will help you stay stone free!

Happy Eating!


14 thoughts on “Top 8 Reasons You Keep Getting Kidney Stones On A Low Oxalate Diet”

  1. I’ve been told I have calcium oxalate crystals in my urine, but I already eat very little meat, chocolate, or many of the other foods listed as causes. I already drink large quantities of water and do not drink soda. I also rarely have dairy due to a lactose intolerance. I do eat lightly salted almonds and drink almond milk frequently, is this enough to cause the crystals? Also, how long for calcium oxalate crystals to pass? Currently only very small crystals with clear to lite yellow urine

    1. Melanie Betz MS, RD, CSR, CSG

      Hi Ashlee! Nutrition is no always the cause of stones – LOTS of other things could be the root cause of what is going on. Every body is different, so it is really hard to know if that is “enough” to cause stones or not. I would suggest checking out this article about good calcium sources for calcium oxalate kidney stones to maybe find a better option than almond milk! The time it takes for stones/crystals to pass is really different based on their size and where exactly they are – so that is a better question for your doctor!

  2. Hi Melanie, thank you for your articles and a great deal of valuable information about kidney stones. I have had kidney stones twice a few years ago. I had a lithotripsy five years ago removed a 8mm stones. Six months ago, the x-ray showed that I had two 4mm stones in my left kidney. According to the 24-hour urine test report, my calcium UR was 364, Ph Ur was 7.1. Brushit was 3.26. The rest of them were within normal. The result is Hypercalciuric Nephrolithis sis. My urologist told me that I could eat anything except anything with Calcium.
    I am confused with his advice.
    Please help. Thank you so much.

    1. Melanie Betz MS, RD, CSR, CSG

      Hi Jean! Thank you for your comment. Avoiding high calcium foods for hypercalicuria is somewhat outdated advice. The American Urological Association recommends making sure calcium intake is adequate for people with high urine calcium for bone health and to help keep urine oxalate low. I would ask your doctor about the recommendation to limit high calcium foods and send them to my site.

  3. I cannot reach the 2.5 liter/QD for urine output. My intake of fluids is 2.5-3.0 liter /QD. According to my Nephrologist, I live in Thailand, my average of 1.5 liters per day is ok. Confusing as the recommendation is clear for 2.5.

    1. Melanie Betz MS, RD, CSR, CSG

      Hi Robb! Everyone is different – and some people are unable to make the recommendation. You just do the best you can!

  4. Thank you! Thank you! and Thank you! This information is amazing and needed. You are doing a great thing by helping people understand what they should and should not do. You have helped me a great deal and I really appreciate it!
    Doing a 48hr urine collection right now and hoping it will be different than 6 months ago where the oxalates in my urine were 4 times higher than normal.
    Again, thank you sooo much Melanie

    1. Melanie Betz MS, RD, CSR, CSG

      Thank you so very much for your comment and for sharing Marcy! It makes my day to hear that my content is actually getting read and is helping people. Good luck getting those oxalates down! Starting to stay away from those really high oxalate foods and getting enough calcium should help!

  5. Valerie Bottega

    Really great content and I LOVE your graphics! As they say, a picture is worth a thousand words, especially for all us visual learners!

    1. Melanie Betz MS, RD, CSR, CSG

      Thank you SO much Valerie! I tend to use my “Mr. McStoney” graphic a lot…mostly because I just LOVE him! haha. I’m glad the graphics are helpful!

  6. Hello Melanie, thank you for another helpful article. I am so relieved to have found your website. There is so much confusing dietary info for new kidney stone patients.

    1. Melanie Betz MS, RD, CSR, CSG

      Thank you very much Kimberly! I’m so happy you find my website helpful. I appreciate you sharing!

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