I get asked about magnesium for kidney stone prevention quite a bit. The short answer is yes, magnesium may help, but I don’t consider it one of the main things most patients should focus on first. And I definitely do not want you running to the 5 and 10 to grab a bottle before you finish this article!
How Magnesium Might Help
Magnesium can bind some oxalate in the gut, which may reduce how much oxalate gets absorbed. It may also make it harder for calcium oxalate crystals to form in the urine. So there is a real reason researchers are interested in it.
What the Research Actually Shows
The problem is that research on magnesium alone is still limited. One recent study found that magnesium citrate taken with meals reduced urine oxalate and calcium oxalate supersaturation in people with already high urine oxalate. That is encouraging, but the study was short and did not tell us whether those patients actually went on to form fewer kidney stones.
You may also hear people mention an older study showing a big reduction in kidney stone recurrence with magnesium. That study is often quoted, but the patients were taking potassium-magnesium citrate, not magnesium alone. That matters because we cannot say that magnesium alone was responsible for the benefit.
Some studies combined magnesium with other nutrients, including vitamin B6. One study used potassium citrate, magnesium citrate, and vitamin B6 together and found a reduction in stone recurrence. Earlier research also examined magnesium oxide combined with vitamin B6. Again, these studies are interesting, but they do not tell us what magnesium alone would have done. And be warned that mag oxide can cause diarrhea!
That distinction matters. It is easy to hear, “There was a magnesium study,” and conclude that everyone with kidney stones should take magnesium. That is not what the research tells us.
Focus on the Basics First
This is why I am careful not to make magnesium sound like a major tool for preventing kidney stones. I actually never discuss it in my patient consults for good reason. Most patients already have plenty to work on, and the things with the strongest evidence still matter most: drinking enough fluids, lowering sodium intake, getting enough dietary calcium, watching added sugars and meat protein, and managing oxalate when needed. These are all the goals of the Kidney Stone Diet®.
Calcium is especially important because it helps bind oxalate in the gut when oxalate is consumed with meals. It also supports bone health, which is another reason I would much rather see patients get their calcium needs met before worrying about adding a supplement.
Who Might Actually Benefit — and What About Magnesium Glycinate?
Could magnesium be useful for some people? Yes. If someone has low urinary magnesium or still has high urine oxalate despite doing the important dietary work, it may be worth discussing this with their doctor.
But magnesium citrate is not automatically appropriate for every stone former. The citrate component can raise urine pH, which may be a problem for some patients already at risk of calcium phosphate stones. This is another reason I do not recommend adding it blindly. Whether it makes sense should be based on the person’s 24-hour urine results, including pH, calcium, citrate, oxalate, and supersaturation of calcium phosphate.
And because I know I will get this question: what about magnesium glycinate? Magnesium glycinate has become a very popular supplement for people who take it at night to relax or wind down. If you are already taking magnesium glycinate for that reason, being a kidney stone former does not automatically mean you need to stop it. Magnesium glycinate does not provide the same citrate load as magnesium citrate, and one study of magnesium glycinate found that it did not raise urine pH or urine citrate the way citrate-containing supplements did.
Taking magnesium glycinate at night because you find it helpful is different from taking it specifically to prevent kidney stones. We simply do not have good evidence that magnesium glycinate prevents stone recurrence. And anyone with significantly reduced kidney function should talk with their physician before taking supplemental magnesium because the kidneys are responsible for clearing magnesium from the body.
Bottom Line
What I do not want is for someone to read about magnesium and think, “Perfect. I’ll just take a pill.”
That is the trap. Supplements can feel much easier than changing sodium intake, increasing fluid intake, getting enough calcium, or adjusting portion sizes. But the pill should not replace the work with the strongest evidence.
For now, magnesium is a possible extra tool for selected patients, not a main prevention strategy for everyone.
Do the big things first. Then let the 24-hour urine tell you whether the smaller things need attention.
Want to Dig Deeper?
2024 randomized controlled trial: Magnesium citrate and magnesium oxide in patients with idiopathic hyperoxaluria. Magnesium citrate taken with meals lowered urinary oxalate and calcium oxalate supersaturation. The study lasted eight weeks and looked at urine chemistry, not long-term stone recurrence.
Potassium-magnesium citrate trial: This frequently cited randomized trial found a substantial reduction in calcium oxalate stone recurrence compared with placebo. However, the treatment combined potassium citrate with magnesium citrate, so the benefit cannot be attributed to magnesium alone.
Potassium citrate, magnesium citrate, and vitamin B6 study: This study used all three together in recurrent stone formers and reported a reduction in stone recurrence. Because it was a combination treatment, it cannot tell us how much benefit was specifically due to magnesium.
Older magnesium and vitamin B6 research: Earlier studies also evaluated magnesium oxide together with vitamin B6 in recurrent calcium oxalate stone formers. Again, this is combination therapy, not evidence that magnesium alone prevents stones.
Your friend,
Nurse Jill
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