THE 2026 RESEARCH FINDINGS - DR. BALDWIN MD
Had a kidney stone? Take a closer look at your supplements.
A new systematic study found that vitamin C supplements increased urinary oxalate—a substance involved in the most common type of kidney stone. Here’s what that may mean for you, in plain English.
In This Guide
Choose a topic to jump to what matters most.
THE FINDING
The short version: supplemental vitamin C raised urinary oxalate.
Researchers combined results from nine intervention studies. Across the evidence, people excreted more oxalate in their urine after taking vitamin C supplements.
9 Studies
+9.72mg
The Average Increase
Two Groups
9 Studies Were Reviewed
Researchers combined findings from nine studies examining how vitamin C supplements affect urine chemistry.
Average increase in 24-hour urinary oxalate compared with participants’ own baseline.
Both Showed An Increase
Increases were observed in people with a history of stones and in people without one.
WHAT IT MEANS
How Vitamin C Can Become Oxalate
Your body uses the vitamin C it needs. Some of the rest can be converted to oxalate and leave through your urine.
1
You Take Vitamin C
It may be in a standalone pill, drink mix, immune product or multivitamin.
KEEP IT IN PERSPECTIVE
2
What this research does—and doesn’t—tell us.
Some Becomes Oxalate
Vitamin C can be metabolized into oxalate inside the body.
Important context: The longest included study lasted six days. The research measured changes in urine—not whether people developed or avoided a kidney stone over the long term.
3
Oxalate Enters Urine
More urinary oxalate may raise calcium oxalate stone risk.
It does not tell us.
That everyone taking vitamin C will develop a kidney stone.
Whether long-term stone recurrence changed.
That CeroMulti itself was tested in these studies.
It does tell us.
Vitamin C supplements increased urinary oxalate on average.
The increase appeared in stone formers and non-stone formers.
Higher supplemental doses tended to produce larger increases.
One quick label check can start a smarter conversation.
Vitamin C can appear in more than one product, so the amounts can add up. Look at multivitamins, immune support products, powders and drinks.
Words to look for:
Vitamin C · Ascorbic Acid · Sodium Ascorbate · Calcium Ascorbate
CHECK YOUR LABEL
HOW CERO MULTIVITAMIN FITS
A physician-formulated multivitamin created for kidney stone formers.
CeroMulti was designed for people who want everyday nutritional support while being thoughtful about ingredients often discussed in kidney-stone care.
QUESTIONS FOR YOUR NEXT APPOINTMENT
Three useful questions to bring with you.
CeroMulti was designed for people who want everyday nutritional support while being thoughtful about ingredients often discussed in kidney-stone care.
01
What type of stone did I have?
Different stone types can call for different nutrition guidance.
02
How much vitamin C am I getting?
Bring photos of every supplement label so your clinician can see the total.
03
Would a 24-hour urine test help?
Ask whether testing could help tailor advice to your individual risk factors.
COMMON QUESTIONS
Common answers — without the jargon.
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Don’t change a supplement prescribed for a medical reason without talking with your clinician. Instead, review your total supplemental amount and your personal stone history with them.
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This review focused on vitamin C supplements. Foods provide vitamin C in a different dietary context and can still be part of a balanced eating pattern. Ask your clinician or dietitian for individualized advice.
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No. It is one risk factor, not a prediction. Hydration, urine volume, sodium, calcium intake, genetics and other factors can also matter.
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No. CeroMulti was not one of the interventions studied. The product connection is that CeroMulti is formulated without added vitamin C.