Excess Urinary Calcium and Kidney Stones Explained

If you’ve been told calcium causes kidney stones, you’ve been misled. In this blog, I break down the real issue behind calcium-based stones: excess urinary calcium combined with oxalate or alkaline urine—not calcium alone. Learn why removing oxalate, not calcium, is the real solution and how a species-appropriate diet plays a critical role in kidney stone prevention.

Key Takeaways:

• Excess urinary calcium alone doesn’t cause kidney stones without oxalate or alkaline urine.

• Calcium actually plays a protective role by reducing urinary oxalate.

• Synthetic calcium supplements and plant-based calcium sources should be avoided.

• Oxalate, not calcium, is the primary driver of calcium oxalate kidney stones.

If you've been suffering from calcium kidney stones, there’s a good chance a doctor told you that calcium was the problem. This could not be further from the truth. Today, I want to dive deep into the real relationship between excess urinary calcium and kidney stone formation.

Calcium kidney stones are by far the most common stone type globally, accounting for about 80% of all stones. Within this, roughly 75% are calcium oxalate stones and about 5% are calcium phosphate stones.

Now, almost every major Urological Association has listed excess urinary calcium as a risk factor. But they’re not giving you the full picture. Let's dig in and expose the real story.

When Calcium Actually Becomes a Risk Factor

Excess calcium alone is not dangerous when it comes to kidney stones. It only becomes an issue under two specific conditions:

First, calcium can be a risk factor when oxalate is present. Calcium and oxalate are like magnets—positively and negatively charged—ready to bind together and form crystals. So, if you eliminate oxalate, the risk disappears. More calcium without oxalate? No problem.

Second, calcium becomes risky when urine pH is alkaline—meaning a pH greater than 7.5. In alkaline urine, calcium favors binding with phosphate over oxalate. That's why mixed stones of calcium oxalate and calcium phosphate often form.

If neither of these conditions is met—no oxalate and neutral or acidic urine—then excess urinary calcium is not a risk factor for kidney stones. 

Why Cutting Calcium is the Wrong Approach

You might be thinking, “I'll just limit calcium in my diet and fix everything!”
That’s a huge mistake. Here's why:

When you cut calcium, you actually increase the amount of oxalate excreted in your urine. Studies show that at 1200 mg of calcium per day (the RDA), you excrete about 2.7 mg of oxalate per 100 mg consumed. Drop your intake to 600 mg of calcium and you now excrete 5.4 mg of oxalate for every 100 mg consumed.

More urinary oxalate = higher kidney stone risk.
Calcium actually plays a protective role by binding oxalate in the gut before it ever reaches your kidneys.

Unfortunately, most people today are woefully deficient in calcium intake, increasing their risk for kidney stones without even realizing it.

The Best Sources of Calcium

Getting your calcium from the right sources is critical.

Bioavailable sources like dairy (milk, cheese, yogurt), bone broth, or supplements like bone matrix powders are ideal.
Avoid plant-derived calcium and synthetic forms like calcium carbonate or calcium citrate.

Synthetic calcium isn’t fully recognized by your body. It gets shuttled off as a waste product, landing in your kidneys—exactly where you don’t want it—and increases the chance of binding with oxalate to form stones.

Managing Calcium Phosphate Stones

If you’re dealing with calcium phosphate stones, urine pH management is key.
These stones form only in alkaline urine.

You want your urine pH between 6.5 and 7.5.

Options include dietary changes (the best and most sustainable), potassium citrate, or other alkalizing agents.
But again, focus on real food first—no fancy supplements needed unless medically necessary.

The Real Solution: Remove Oxalate

For calcium oxalate stones, it’s not about the calcium.
It’s about removing oxalate from your diet.

If you eliminate oxalate, calcium oxalate stones cannot form—period.
The only exception to this is the extremely rare genetic condition called primary hyperoxaluria type 1, where the liver produces oxalate internally.

For the rest of us, dietary oxalate is the true villain.
And unfortunately, low oxalate diets are not enough for many people because oxalate is cumulative in the body. Your intake does not match your output, and oxalate can linger in joints, glands, and kidneys for days, weeks, or even longer.

Zero oxalate is the goal for long-term kidney stone freedom.

The Role of Ancestral Diets and Metabolic Health

If you're forming kidney stones, it’s likely you lack the genetic machinery to process oxalate properly.
Somewhere in our ancestral line, we didn’t evolve to eat high-oxalate plant foods. Other populations did. That’s why some people can drink spinach smoothies daily and never get a stone—we can’t.

Also, don’t ignore the huge role of metabolic dysfunction.
Roughly 87% of Western adults suffer from metabolic issues today, primarily due to poor diet choices—high in sugar, processed foods, and inflammatory ingredients.

Fix your diet, fix your stones.

How to Move Forward

If you want to stop forming calcium-based kidney stones:

• Eliminate oxalate from your diet completely.

• Ensure daily calcium intake hits 1200 mg from bioavailable food sources.

• Manage urine pH if dealing with calcium phosphate stones.

• Focus on a nutrient-rich, species-appropriate diet—animal foods first, with limited seasonal fruit if tolerated.

Kidney stones are beatable. You just have to get to the real root cause—and calcium isn’t it.