Urine Uric Acid-Creatinine Ratio Calculator

Calculate the random urine uric acid-creatinine ratio in mg/mg with the mmol/mmol equivalent at every threshold, against the 1.0 cutoff used to recognise acute urate nephropathy in tumour lysis syndrome.

Last updated 17 Sep 2026

Urine Uric Acid-Creatinine Ratio

Uric acid ÷ creatinine

Urine uric acid (mg/dL)Random urine uric acid in mg/dL. If your report is in mmol/L, multiply by 16.81 to get mg/dL — 1 mmol/L is 16.81 mg/dL.

Urine creatinine (mg/dL)From the same sample, in mg/dL. If your report is in mmol/L, multiply by 11.31 to get mg/dL — 10 mmol/L is 113 mg/dL.

0.70mg/mgExample

Urine uric acid 42 mg/dL, urine creatinine 60 mg/dL

Formula

Ratio (mg/mg) = urine uric acid (mg/dL) ÷ urine creatinine (mg/dL)
Ratio (mmol/mmol) = ratio (mg/mg) × 0.673
Adult reference 1.0 mg/mg supports acute urate nephropathy

× 0.673: mg/mg to mmol/mmol, being creatinine’s molecular mass over urate’s, 113.12 over 168.11. The reciprocal is 1.486. So the adult reference limit of 0.60 mg/mg is 0.40 mmol/mmol and the nephropathy threshold of 1.0 mg/mg is 0.67 mmol/mmol — a ratio quoted as 0.67 could be either the SI threshold or a mid-range conventional result
> 1.0 mg/mg: quoted as consistent with acute uric acid nephropathy in a patient with acute kidney injury; below 0.75 mg/mg is quoted as consistent with other causes of acute renal failure. The band between them is genuinely indeterminate
children: ratios are far higher and fall with age — the 5th to 95th centile range is roughly 1.19 to 2.38 mg/mg under six months, 0.59 to 1.64 at three to five years, and 0.30 to 0.59 at 14 to 17 years. The adult cutoffs simply do not apply
stone disease: the ratio screens for urate overexcretion, but the main determinant of uric acid stone formation is urine pH: urate is poorly soluble below pH 5.5 and highly soluble above 6.5. Measure the pH
the other use: as a stand-in for 24-hour urate excretion where a timed collection is impractical, which in practice means small children

Worked example

Urine uric acid 42 mg/dL, urine creatinine 60 mg/dL
42 ÷ 60 = 0.70 mg/mg
0.70 × 0.673 = 0.47 mmol/mmol
Above the adult reference limit of 0.60 mg/mg, below the 0.75 used to argue against urate nephropathy
Not diagnostic either way — in acute kidney injury it is the setting, the serum urate and the phosphate that decide
In a two-year-old the same 0.70 would sit inside the reference range for that age

Thresholds, in both unit systems

Multiply mg/mg by 0.673 for mmol/mmol, and mmol/mmol by 1.486 to go back. A ratio quoted bare as 0.67 is ambiguous: it is the SI nephropathy threshold, and it is also an unremarkable conventional result.
Threshold	mg/mg	mmol/mmol	Meaning
Adult upper reference limit	0.60	0.40	Above this is urate overexcretion for an adult
Against urate nephropathy	< 0.75	< 0.50	Quoted as consistent with other causes of acute renal failure
Supports urate nephropathy	> 1.00	> 0.67	In a patient with acute kidney injury, classically tumour lysis syndrome

Paediatric reference ranges (5th–95th centile, mg/mg)

Converted at 0.673 mmol/mmol per mg/mg. A ratio of 1.5 is markedly abnormal in an adult and unremarkable in a six-month-old. The fall with age is largely the rising creatinine denominator, together with maturation of tubular urate handling.
Age	mg/mg	mmol/mmol
Under 6 months	1.19 – 2.38	0.80 – 1.60
6 to 12 months	1.04 – 2.23	0.70 – 1.50
1 to 3 years	0.70 – 2.08	0.47 – 1.40
3 to 5 years	0.59 – 1.64	0.40 – 1.10
5 to 7 years	0.45 – 1.19	0.30 – 0.80
7 to 10 years	0.39 – 0.83	0.26 – 0.56
10 to 14 years	0.30 – 0.65	0.20 – 0.44
14 to 17 years	0.30 – 0.59	0.20 – 0.40

One ratio, two questions, and a unit trap

The random urine uric acid-creatinine ratio does two jobs that are easy to confuse. In a patient with acute kidney injury it is a discriminator: a ratio above 1.0 mg/mg supports acute uric acid nephropathy, while a ratio below 0.75 mg/mg is quoted as consistent with other causes of acute renal failure. In a patient with stones or a suspected metabolic abnormality it is a screen for urate overexcretion, read against an adult reference limit of 0.60 mg/mg, and a stand-in for a 24-hour urate collection where a timed sample is impractical — which in practice mostly means small children. Dividing by creatinine is what makes a spot sample interpretable: a urine concentration on its own says as much about how much the patient drank as about what the kidney did.

The unit trap matters. Converting mg/mg to mmol/mmol means multiplying by 0.673, the molecular mass of creatinine over that of urate, 113.1 over 168.1. So 1.0 mg/mg is 0.67 mmol/mmol, and 0.60 mg/mg is 0.40 mmol/mmol. A ratio reported as 0.67 is therefore either the SI threshold for urate nephropathy or an unremarkable conventional result, depending entirely on a unit that is frequently omitted from a handover or a textbook table. This page prints both at every threshold for that reason.

The setting where the high threshold earns its keep is tumour lysis syndrome. Within hours to days of treating a bulky, rapidly proliferating malignancy — Burkitt lymphoma, acute lymphoblastic leukaemia, high-grade lymphoma — cell breakdown releases nucleic acids, potassium and phosphate. Urate rises steeply and precipitates in the acid environment of the distal tubule and collecting duct, obstructing them and causing oliguric acute kidney injury; calcium phosphate deposition compounds the damage. A urine urate-creatinine ratio above 1.0 fits that mechanism and argues against a coincidental pre-renal or nephrotoxic cause. It should not delay treatment: fluids to establish a high urine output, rasburicase where the urate is high and the risk substantial, allopurinol for prophylaxis, careful attention to potassium, phosphate and calcium, and early renal support if oliguria persists.

In stone disease the ratio deserves less weight than it often gets. Urate overexcretion contributes to uric acid stones and to calcium oxalate stones, but the dominant determinant of uric acid stone formation is urine pH: urate is poorly soluble below pH 5.5 and highly soluble above 6.5, which is why alkalinisation dissolves uric acid stones while allopurinol alone often does not. A normal ratio with a persistently acid urine still identifies a uric acid stone former. And in children the adult thresholds are simply the wrong yardstick — the reference range under six months runs to 2.38 mg/mg, four times the adult limit. This calculator supports a clinician’s assessment and does not replace it.

Frequently asked questions

What urine uric acid-creatinine ratio suggests acute urate nephropathy?

A ratio above 1.0 mg/mg, which is 0.67 mmol/mmol, in a patient with acute kidney injury is quoted as consistent with acute uric acid nephropathy, while a ratio below 0.75 mg/mg is quoted as consistent with other causes. The setting — usually tumour lysis syndrome after treatment of a bulky malignancy — carries as much weight as the number.

What is the normal urine uric acid-creatinine ratio in adults?

Below about 0.60 mg/mg, or 0.40 mmol/mmol. Children are much higher at every age and fall towards the adult figure through adolescence: the 5th to 95th centile range is roughly 1.19 to 2.38 mg/mg under six months and 0.30 to 0.59 mg/mg at 14 to 17 years.

How do I convert the ratio between mg/mg and mmol/mmol?

Multiply mg/mg by 0.673 to get mmol/mmol, and multiply mmol/mmol by 1.486 to go back. The factor is creatinine’s molecular mass over urate’s, 113.1 over 168.1. So 1.0 mg/mg is 0.67 mmol/mmol and 0.60 mg/mg is 0.40 mmol/mmol.

Does a normal ratio rule out uric acid stones?

No. The main determinant of uric acid stone formation is a persistently acid urine rather than the amount of urate excreted — urate is poorly soluble below pH 5.5 and highly soluble above 6.5. A patient with a normal ratio and a urine pH of 5.2 is still at risk, and alkalinisation is the treatment that matters.

Should the ratio be checked before giving rasburicase?

It should not delay it. If tumour lysis syndrome is likely and the urate is high, treatment — fluids, rasburicase where indicated, monitoring of potassium, phosphate and calcium — comes first. Note also that rasburicase continues to degrade urate in the specimen at room temperature, so samples for urate after dosing must be transported on ice or the result will read falsely low.

Related calculators

References

Kjellstrand CM, Cambell DC, von Hartitzsch B, Buselmeier TJ. Hyperuricemic acute renal failure. Arch Intern Med. 1974;133(3):349–359.
Coiffier B, Altman A, Pui CH, et al. Guidelines for the management of pediatric and adult tumor lysis syndrome: an evidence-based review. J Clin Oncol. 2008;26(16):2767–2778.
Mayo Clinic Laboratories. Uric acid/creatinine ratio, random, urine — reference values and interpretation. Test catalogue, 2025.
Stapleton FB, Linshaw MA, Hassanein K, Gruskin AB. Uric acid excretion in normal children. J Pediatr. 1978;92(6):911–914.

Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.