Calcium Oxalate Crystals in Urine

Roughly 10% of people will develop kidney stones in their lifetime. And around 70% of those affected may struggle with recurrence. 

Approximately 80% of kidney stones are calcium-based. 

Calcium oxalate stones occur in 80% of these cases, making them the most widespread type of kidney stones. (1)

Research shows that calcium oxalate stones tend to be recurrent. There is a 10-year recurrence rate of 30% in patients that had these stones for the very first time. 

Before you can figure out how do you flush oxalates out of your body, it’s important to get a better perspective of what calcium oxalate kidney stones are and how they affect the body. (2)

What Are Calcium Oxalate Kidney Stones?

Oxalates and kidney stones go hand in hand. Calcium oxalate stones are tough clumps of minerals and other substances. They are the most prevalent type of kidney stone. 

Kidney stones are solid masses that emerge in the kidneys when the calcium levels get high. Or there are high cystine, oxalate, or phosphate levels and insufficient liquid. 

So, what are calcium oxalate crystals? Calcium oxalate is often the result of excess oxalate in the urine. This causes the oxalate to clump together and crystalize into kidney stones. 

A normal urine oxalate excretion level is less than 45mg per day. A higher level could indicate that you are at risk of kidney stones

But, the odds of stone formation could go up even in patients with levels over 25 mg daily, which is considered normal. Consuming foods packed with vitamin C could impact the urine sample. Bowel inflammation from the colon or intestinal surgery could also raise the oxalate in the urine. 

Symptoms of calcium oxalate stones

Calcium oxalate stones symptoms are sometimes tricky to spot. You might not notice the calcium oxalate stone until it starts moving through the urinary tract. When calcium oxalate crystals move, they can cause intense pain and discomfort. 

Oxalates crystals can result in symptoms such as:

  • Pain in the back and side that’s usually powerful and comes in waves
  • Blood in the urine (making the urine look brownish, pink, or red)
  • Pain when peeing
  • Urine with a bad odor
  • Cloudy urine
  • Vomiting and nausea
  • A constant need to pee
  • Chills and fever for those that struggle with an infection



Both environmental factors and genetic predisposition can lead to stone formation. Genes are typically responsible for the heritable aspect of oxalate crystal formation. 

So, what causes calcium kidney stones other than the genes? The urine has a chock-full of chemicals capable of preventing oxalate from clumping together and creating oxalate crystals. 

But, the stones can form when there is little urine and excess oxalate. Typical causes of oxalate crystals in the urine are:

To know how to flush oxalates from the body, you need to drink fluids. But, a 2022 report indicates that 75% of people in the United States are chronically dehydrated. Dehydration is a typical complaint among the elderly, reported to occur in 17-28% of older adults in the country. (3)

Water aids in dissolving antibiotics for treating urinary tract infections. It is making the body create more urine to get rid of germs. When you pair dehydration with a diet high in oxalate, salt, and protein, that’s when kidney stones can become a real problem. 

Other factors can make you more prone to calcium and kidney stones. Such as:

  • Obesity
  • Diabetes
  • Weight reduction gastric bypass surgery
  • Inflammatory bowel disease
  • High parathyroid hormone (hyperparathyroidism)
  • Dent disease 

Does Calcium Cause Kidney Stones?

Can calcium cause kidney stones? The type of kidney stones you have will impact the food choices you make. When it comes to oxalate and calcium, patients worry about dairy and milk spurring more kidney stones to develop.  

Although calcium sounds like it would be causing calcium kidney stones to form, that’s not the case. When taken in proper amounts (1,200 mg a day), calcium could hinder other substances in the digestive tract that might result in stones. The calcium should come from food. 

Plus, those with calcium oxalate kidney stones still require a proper amount of calcium in their system. Instead of limiting the calcium, it’s more practical to focus on a low oxalate kidney stone diet. Contact your doctor about calcium stones and whether you should be making any dietary changes. 

They may suggest you obtain calcium from plant-based and low-oxalate consumables like veggies, cereals, some beans, etc. A dietitian can also help you make a list of high oxalate foods to include or avoid. 

cruciferous vegetables

What Foods Contribute to Calcium Oxalate Kidney Stones?

Calcium oxalate stones prevention starts with a healthy diet. But, what is oxalate in food? Oxalic acid (oxalates) is a naturally-occurring compound in plants. Many consumables high in oxalates are healthy, such as legumes and leafy greens. However, oxalates can bind to calcium, amplifying the odds of kidney stones in certain patients. 

  • An unhealthy high oxalate food list starts with an excess amount of sugar, sodium (salt), oxalate, and too much protein. When you try to limit the high oxalate diet, it’s best to steer clear of fast foods, packaged, and canned products. As well as several types of meat, seasonings, and condiments. 

Based on one study, eating more sodium was linked with an 11-61% increased risk of kidney stones. With a more notable effect in female patients. While drinking more water led to a reduced risk of kidney stone formation from 13-31%. (4)

Of course, sodium is not the only culprit. You would need to remain hydrated and manage the sugar intake. But, most importantly, you need to be familiar with an oxalates diet. There are plenty of oxalate-rich foods to avoid. Classic examples of oxalate foods to avoid for kidney stones are: 

  • French fries
  • Rhubarb
  • Spinach
  • Potato chips
  • Bran flakes
  • Beets

A moderate intake of this oxalate foods list could be beneficial. But, it’s best to talk to a specialist to avoid going overboard with your oxalate diet. That’s because too much dietary oxalate can bind the excess oxalate to minerals like calcium. Thus, preventing the system from absorbing a sufficient amount of nutrients. 

What Foods Should You Eat if You Have Calcium Oxalate Kidney Stones?

To give your kidneys a healthy boost, you may need to adjust the calcium oxalate in your kidney stones diet. The majority of plant-based products are packed with oxalates. But, they also have a chock-full of minerals and vitamins. 

So, what’s the trick to eating the right diet for calcium oxalate stones?

The goal is simple – balance the oxalate-rich foods list with other veggies and fruits. That way, you can get enough nutrients that can benefit the kidneys. Adequate lifestyle choices paired with healthy eating can curb the impact oxalates have.

You would need to:

  • Drink plenty of water
  • Manage the calcium intake
  • Get enough vitamin C
  • Cook veggies with low oxalate content

Now, the first thing you will come across is the oxalate foods to avoid. But, which ones should you eat? Here is an oxalate list of foods that can come in handy in a low-oxalate diet. This oxalates foods list can include:

  • Proteins: poultry, fish, eggs
  • Fruits: peaches, lemons, apples, cherries, blackberries, etc.
  • Veggies: cabbage, cauliflower, zucchini, peas, etc.
  • Dairy: butter, milk, cheese, yogurt, etc.
  • Drinks: fruit juice, water, and coffee. 
  • Herbs: cumin, turmeric, cinnamon, etc.

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Stones smaller than 4 mm pass without treatment 80% of the time. They need about 31 days to leave the system. Stones 4 to 6 mm in size may require treatment. However, roughly 60% of them don’t, which can take about 45 days to pass.

The calcium oxalate stones treatment will vary based on what’s causing the problem. If there is a low urine volume, patients can increase their fluid intake to 2.5 to 3.0 L/d. Others will need to go easy on the salt and up their dietary calcium intake. 

If there is pain and discomfort, some patients receive pain meds. This mainly includes the use of ibuprofen or naproxen sodium. This calcium oxalate kidney stone treatment can relieve aches and curb discomfort. 

When the low oxalate diet is not enough, medical therapy becomes a go-to choice. Patients could use meds to help the system pass the kidney stones. These are alpha-blockers that can relax the ureter muscles and ease the pain. This kind of treatment of calcium oxalate kidney stones is for small stones.

For a large stone that’s triggering symptoms, more invasive treatment may be necessary. This includes surgery (percutaneous nephrolithotomy), using sound waves for breaking the stones up (extracorporeal shock wave lithotripsy (ESWL) ), or scope to get rid of the stones (ureteroscope). But, only a doctor can recommend the ideal calcium oxalate stones treatment. 

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How Do You Get Rid of Calcium Oxalate Kidney Stones?

When dealing with oxalates and kidney stones, your diet and lifestyle remain key components in your recovery. You need to be familiar with the high oxalate foods to avoid as well as which foods to include. Crystallized kidney stones could leave the system without treatment in roughly 4 to 6 weeks. 

To do that, you would need to drink a lot of water. Dietary management can help prevent the existing stones from growing in size. It can also help you avoid new stones from forming. Doctors may sometimes prescribe Flomax (tamsulosin) or Cardura (doxazosin). 

These meds can relax the ureter and let the crystalline kidney stones pass quicker. To get rid of the oxalate kidney stones, you will:

  • Consume a minimum of 8 to 12 cups of fluid daily.
  • Eat 3 to 4 servings of non-fat or low-fat dairy foods daily.
  • Limit the sodium intake to less than 3,000 mg daily.
  • Avoid supplements that have well over 500 mg of vitamin C daily.
  • Know which oxalate-rich foods to avoid.
  • Curb the extra weight. 
  • Reduce alcohol intake. 

Planning your diet

To stay on the right track with your eating habits, it’s best to plan your plate for kidney stones. A nutritionist can help you customize the dietary regimen based on your blood tests, urine sample, and medical ailment.  

Overall, your plate can consist of 2 cups of raw or 1 cup of cooked veggies for lunch and dinner. One to two servings of fruits, starches, and grains, including 2 to 4 ounces of lean protein. You can consume products like lemonade, beer, wine, buttermilk, etc, as well as foods like parsnips, lima beans, lettuce, etc. 

If you recognize the symptoms or you had calcium oxalate kidney stones in the past, book an appointment with your urologist or primary care physician. The doctor can pinpoint any issues in your diet or lifestyle that could be a contributing factor. They can also provide you with adequate treatment and healthcare to prevent the stones from getting bigger.


Calcium oxalate stones are a typical occurrence. They are a widespread type of kidney stones that look like solid masses. 

They are the result of extra oxalate in the urine. But, there are many other calcium oxalate stones causes. 

These stones can trigger pain and lead to complications, such as urinary tract infections. It’s important that you spot the symptoms and seek treatment when necessary. 

Consult a nutritionist about whether you need an oxalate-free diet, or you should reduce the oxalates with proper food choices. 

Although the treatment will vary, people often need to readjust their diet, fluid intake, and lifestyle. Talk to a specialist to get your kidney function back on track and treat the underlying problem.

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  1. Finkielstein VA, Goldfarb DS. Strategies for preventing calcium oxalate stones. CMAJ. 2006.
  2. O’Kell AL, Grant DC, Khan SR. Pathogenesis of calcium oxalate urinary stone disease: species comparison of humans, dogs, and cats. Urolithiasis. 2017.
  3. Taylor K, Jones EB. Adult Dehydration. [Updated 2022 May 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:
  4. Sorensen MD, Kahn AJ, Reiner AP, et al. Impact of nutritional factors on incident kidney stone formation: a report from the WHI OS. J Urol. 2012.

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