Overview
Twenty-four hours of urine, collected into a jug, tells us the chemistry that drives your stones. Nothing else does.
A spot sample cannot. Stone formation depends on how concentrated your urine is and how much of each substance passes through it across an entire day — including the overnight hours when urine is most concentrated and crystals most readily form.
What we measure and why each one matters
Volume. The single most important number. Below two and a half liters, everything else is harder to fix. Most stone formers are chronically under hydrated and do not believe they are.
Calcium. High urinary calcium is the most common abnormality in calcium stone formers. Dietary sodium drives it, which is why salt restriction lowers urine calcium.
Oxalate. Binds calcium to form the most common stone. Raised by spinach, nuts, chocolate, and — counterintuitively — by restricting dietary calcium, which frees oxalate for absorption.
Citrate. The body's natural stone inhibitor. It binds calcium in urine so it cannot crystallize. Low citrate is common and highly treatable with potassium citrate.
Uric acid. Drives uric acid stones and promotes calcium oxalate crystallization.
pH. Persistently acidic urine forms uric acid and cystine stones. Persistently alkaline urine forms calcium phosphate and struvite stones. This single value redirects the entire strategy.
Sodium. A proxy for dietary salt, and the lever that lowers urinary calcium.
Creatinine. Not a target — a quality check. It tells us whether you actually collected the full 24 hours.
| What it measures | Why it matters |
|---|---|
| Total protein | Quantifies kidney damage a single sample can't |
| Creatinine clearance | Estimates true filtering capacity |
| Stone-forming chemicals | Guides prevention for recurrent kidney stones |
Why this is where prevention starts
Without it, prevention is guesswork. The recurrence rate after a first stone is roughly fifty percent within five to ten years. Targeted treatment based on this collection drops it substantially.
And the treatments diverge completely by mechanism. High urine calcium calls for a thiazide. Low citrate calls for potassium citrate. High uric acid with acidic urine calls for alkalinization and sometimes allopurinol. Give the wrong one and you have treated nothing.
Doing the collection correctly
Discard the first morning void. Note the time — that is your start. Collect every drop for the next twenty-four hours, including the first void of the following morning, which ends the collection.
Keep the container refrigerated or on ice. Missing a single void invalidates the entire study, and the creatinine will usually reveal that it happened.
Collect during an ordinary week. Not while traveling, not while sick, not after a holiday. We want your real chemistry, not a snapshot of an unusual few days.
Repeating it
We collect once at baseline, again several months after starting treatment to confirm the chemistry actually moved, and periodically thereafter.
That second collection is the one people skip. It is also the one that tells us whether the treatment is working, because stones take years to recur and waiting for one is a poor way to find out.