Ramadan Fasting Raises Urinary Citrate But Doesn't Increase Kidney Stone Risk: What the Research Shows

Ramadan Fasting Raises Urinary Citrate But Doesn't Increase Kidney Stone Risk: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Ramadan fasting is one of the largest natural experiments in intermittent fasting: hundreds of millions of people abstain from food and water from dawn to sunset for a full month every year. Researchers wanted to know whether the dehydration and altered eating window that comes with this daily extended fast changes the urine chemistry that drives kidney stone formation — specifically calcium, oxalate, citrate, and uric acid levels. This adds useful data to the broader question covered in is intermittent fasting safe for people worried about kidney stones and how fasting affects kidney health.

Who Was Studied

Participant profile: All 57 participants were men aged 30 to 55. Thirty-seven had a documented history of recurrent calcium-based kidney stones; the remaining 20 had no history of urinary calculi. All underwent blood tests, renal ultrasonography, urinalysis, and urine culture in addition to the 24-hour urine chemistry panel.

How Ramadan fasting worked in this study: Participants abstained completely from food and fluids from dawn until sunset every day for the entire lunar month, then ate and drank normally during the evening and overnight hours — a pattern of daily prolonged fasting lasting roughly 13-17 hours depending on the season and location. Researchers collected 24-hour urine samples once before Ramadan began (baseline, nonfasting) and again during the fasting month, measuring calcium, oxalate, citrate, uric acid, magnesium, phosphate, sodium, potassium, and creatinine each time.

What the Researchers Found

Urinary citrate and uric acid concentration

• Citrate is a natural stone inhibitor, so a rise in its urine concentration during fasting is a favorable, not a harmful, change.
• Urine became more concentrated overall during the fasting days, which explains why several solutes measured higher per liter even though total daily output of some of them fell.
• The most clinically important single finding: despite these concentration shifts, calcium oxalate supersaturation — the actual physical-chemical measure of stone-forming risk — did not rise significantly during fasting.

Total 24-hour excretion and volume

• Total urine volume was lower during fasting days than during the nonfasting baseline period, consistent with the shortened window for fluid intake.
• Total 24-hour excretion of calcium, phosphate, and magnesium was lower during fasting than nonfasting, tracking the reduced fluid load and altered meal timing rather than any change in kidney handling of these minerals.
• Uric acid supersaturation was somewhat accentuated during the fasting period, a change the authors linked to urine concentration rather than a true increase in uric acid production.

What Did Not Change

• Calcium oxalate supersaturation — the primary chemical driver of the most common type of kidney stone — showed no significant increase during fasting.
• The overall pattern did not point to a meaningful rise in stone-forming risk between the recurrent stone formers and the comparison group with no stone history.

What the Researchers Concluded

The authors concluded that although Ramadan fasting produces measurable shifts in urine concentration and composition — including a favorable rise in the stone-inhibitor citrate — there was not enough evidence to say that fasting increases the risk of urinary calculus formation, even among men with a prior history of recurrent stones.

What This Means If You Fast

• Citrate rising is a good sign, not a bad one. Citrate binds calcium in urine and blocks crystal growth, so seeing it increase during a fasting window is reassuring rather than concerning for stone risk, as also discussed in the safety profile of intermittent fasting for kidney stone risk.
• Hydration timing still matters. Because total urine volume dropped during the fasting hours, front-loading fluids and electrolytes during the eating window is a sensible precaution — see electrolytes and intermittent fasting for practical guidance.
• This was daily prolonged dawn-to-dusk fasting, not typical 16:8 time-restricted eating. Ramadan fasts run considerably longer than most intermittent fasting windows practiced outside of religious observance, so the fluid-restriction effect seen here may not fully apply to shorter eating windows.
• People with a stone history were not shown to be at added risk in this small sample. The recurrent stone formers in this study did not show a clearly worse metabolic profile than the comparison group during fasting, but this is not a guarantee for every individual — those with a personal or family history of stones should still discuss fasting with a physician, as outlined in how fasting interacts with kidney health more broadly.
• Uric acid concentration rising deserves attention for gout-prone individuals. Even though overall stone risk markers were reassuring, the uric acid supersaturation increase suggests people prone to uric acid stones or gout flares may want to prioritize fluid intake specifically.

Study Limitations

• Small sample (57 total participants, 37 in the stone-former group and 20 in the comparison group) limits statistical power and generalizability.
• All-male cohort — findings cannot be assumed to apply to women, whose baseline urinary citrate and stone risk profiles differ.
• Before-and-after (non-randomized) design without a non-fasting control group followed over the same calendar period, so seasonal and dietary factors during Ramadan cannot be fully separated from the fasting effect itself.
• Only urine chemistry and supersaturation indices were measured — the study did not track actual new stone formation or stone-related hospital visits during or after the fasting month.
• Population and climate specific to Iran; heat, humidity, and typical Ramadan meal composition (timing of salt, protein, and fluid intake at the pre-dawn and post-sunset meals) vary substantially by country and could change the results elsewhere.
• Funding source was not reported in available summaries, and the full-text methodology could not be independently verified from PubMed at the time this article was written.

Source

Miladipour, A. H., Shakhssalim, N., Parvin, M., & Azadvari, M. (2012). Effect of Ramadan fasting on urinary risk factors for calculus formation. Iranian Journal of Kidney Diseases, 6(1), 33–38. PMID: 22218117

Frequently Asked Questions

Does intermittent fasting cause kidney stones?

There is no strong human evidence that intermittent fasting causes kidney stones. This 2012 study of 57 men found that Ramadan's daily prolonged fast changed urine concentration but did not significantly raise calcium oxalate supersaturation, the main chemical driver of the most common stone type.

Does Ramadan fasting increase kidney stone risk?

The research is mixed but leans toward "no meaningful increase" for otherwise healthy fasters. This study found urinary citrate — a stone inhibitor — actually rose during fasting, and stone-forming supersaturation indices did not significantly worsen, though other retrospective studies have found seasonal upticks in renal colic visits, particularly in hot climates.

What happens to urinary citrate during fasting?

In this study, urinary citrate concentration rose significantly during the Ramadan fasting period compared to the nonfasting baseline. Since citrate binds calcium and inhibits crystal formation, higher urinary citrate is generally protective against stone formation rather than a risk factor.

Is time-restricted eating safe for people with a history of kidney stones?

This study's 37 recurrent stone formers did not show a clearly elevated risk profile during fasting compared to the 20 participants with no stone history, but the sample was small and all-male. Anyone with a personal history of kidney stones should discuss any fasting protocol with a urologist or nephrologist before starting.

How much water should I drink while intermittent fasting to avoid kidney stones?

This study found total urine volume dropped during the fasting hours, so prioritizing fluid intake during the eating window is a reasonable precaution. General stone-prevention guidance recommends enough fluid to produce roughly 2 to 2.5 liters of urine per day, concentrated into the hours available for drinking during a fasting protocol.

Related Research and Articles

• Is Intermittent Fasting Safe for People With Kidney Stones?
• How Fasting Affects Kidney Health
• Ramadan Fasting vs. Intermittent Fasting
• Electrolytes and Intermittent Fasting
• Alternate-Day Fasting: The Complete Guide
• Time-Restricted Eating: The Complete Guide
• Research: Early Time-Restricted Eating for Weight Loss

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