Lemon water does measurably raise urinary citrate, and citrate is a genuine inhibitor of calcium crystal formation. In a 2026 randomised trial it raised citrate by about 168 mg a day. But whether that helps depends on which stone you form — and for calcium phosphate stones, a review concludes the net effect is still undetermined.
What was measured
The APUL randomised crossover trial, published in 2026, tested four drinks against 24-hour urine chemistry. Two moved citrate:
- Lemon water: +168 mg/day (95% CI 16 to 319)
- Coconut water: +274 mg/day (95% CI 68 to 480)
Apple cider vinegar, tested in the same trial, changed nothing measurable.
Twenty participants, one week per drink, and none of them had ever formed a stone. Small, short, and in the wrong population — so read it as a signal about urine chemistry rather than proof about stones.
Why citrate matters
Citrate is not a folk remedy. It is one of the better-understood inhibitors in stone formation, and it works through several mechanisms at once: it forms soluble complexes with calcium, and it interferes with crystal nucleation, growth, and aggregation.
Low urinary citrate — hypocitraturia — is a common finding on 24-hour collections, and it is one of the specific abnormalities a metabolic evaluation looks for.
Why your urine pH complicates this
Here is the part most coverage of lemon water leaves out.
Citrate excretion is largely governed by acid-base balance: acidity is the main determinant of how much citrate ends up in urine. Anything that provides citrate also tends to provide an alkali load, which raises urine pH.
For calcium oxalate stones, raising pH is broadly not a problem. For calcium phosphate stones it can be, because calcium phosphate forms more readily in alkaline urine. A 2019 review of citrate therapy in calcium phosphate stones describes exactly this tension — potassium citrate raises citrate and lowers urinary calcium, both helpful, while also pushing pH in an unhelpful direction — and concludes that the net clinical effect on calcium phosphate stone formation remains to be determined.
So "citrate is good, lemons have citrate, drink lemon water" is true in each clause and not necessarily true as a conclusion. It depends on your stone.
Low citrate has causes worth knowing
The same literature lists reasons citrate runs low, and several are not dietary:
- distal renal tubular acidosis
- low potassium
- diets high in animal protein
- diets low in alkali
- certain medications, including acetazolamide, topiramate, ACE inhibitors, and thiazides
That last group matters. If your citrate is low and you take one of those, it is a conversation with your prescriber rather than a lemonade problem.
One note on harms
The 2026 systematic review, which pooled 31 studies, recorded that there may be increased minor adverse events with lemon juice — rated low strength of evidence, and minor rather than serious. Nothing alarming. But it is the only entry on its harms list attached to a dietary measure people assume is free of downside, so it is worth stating.
What this does not tell you
How much, or whether. Prescription potassium citrate is a different thing at a different dose, and lemon juice is not a substitute for it.
If your own 24-hour collection shows low citrate, that is a specific finding with well-studied management options. If you do not know your citrate, that is the question worth answering before this one.