Urine Homovanillic Acid (HVA) Unit Converter
Urine Homovanillic Acid (HVA) Unit Converter
HVA is the dopamine metabolite and half of the neuroblastoma pair. Convert mg/24 h, µg/24 h, µmol/24 h and nmol/24 h — and note that Mayo and ARUP disagree twofold.
Urine Homovanillic Acid (HVA) converter
Mass ⇄ molar, per 24 hA 24-hour urinary HVA of 8.0 mg in an adult
Formula and conversion factors
nmol/24 h = µg/24 h × 5.48929
mg/24 h = µmol/24 h ÷ 5.48929
- 182.173
- the molecular weight of homovanillic acid, C9H10O4 (PubChem CID 1738; HMDB gives 182.1733)
- 5.48929
- µmol per mg. Larger than VMA’s 5.05 because HVA is the lighter molecule by one oxygen — the two factors are not interchangeable
- mg/g creatinine
- how paediatric HVA is reported. ARUP gives 0 to 42 mg/g for ages 0 to 2 and 0 to 8 mg/g for adults; a ratio, not an excretion
Worked example
A 24-hour urinary HVA of 8.0 mg in an adult
8.0 × 5.48929 = 43.9 µmol/24 h
= 43,914 nmol/24 h
At Mayo's upper limit of 8.0 mg/24 h, but barely half of ARUP's 15.0 mg/day
One result, two verdicts: a figure of 10 mg/day is raised at Mayo and normal at ARUP, so the source of the interval has to be quoted with it
Urine HVA: a twofold disagreement between laboratories
| Source | Limit | Unit |
|---|---|---|
| Mayo HVA, 15 years and over | < 8.0 | mg/24 h |
| The same limit in SI | < 43.9 | µmol/24 h |
| ARUP, 18 years and over | 0.0 – 15.0 | mg/day |
| The same limit in SI | 0.0 – 82.3 | µmol/day |
| ARUP, ratio to creatinine, adult | 0 – 8 | mg/g creatinine |
| ARUP, ratio to creatinine, 6 – 17 years | 0 – 15 | mg/g creatinine |
| ARUP, ratio to creatinine, 0 – 2 years | 0 – 42 | mg/g creatinine |
| Mayo, under 1 year | < 35.0 | mg/g creatinine |
HVA and VMA: why both are measured
| HVA | VMA | |
|---|---|---|
| Parent amine | Dopamine | Adrenaline and noradrenaline |
| Molecular weight | 182.173 | 198.173 |
| µmol per mg | 5.48929 | 5.0461 |
| Raised in neuroblastoma | Often, sometimes alone | Often, sometimes alone |
| Useful for phaeochromocytoma | No | No — metanephrines are the test |
| Adult upper limit, Mayo | 8.0 mg/24 h | 8.0 mg/24 h |
| Adult upper limit, ARUP | 15.0 mg/day | 7.0 mg/day |
The dopamine metabolite, and the twofold question it raises
Homovanillic acid is to dopamine what VMA is to adrenaline and noradrenaline: the terminal product of sequential O-methylation and oxidative deamination, excreted in the urine in amounts that track dopamine turnover. It is the reason a neuroblastoma work-up asks for two metabolites rather than one. These tumours arise anywhere along the sympathetic chain and differ in how far they take catecholamine synthesis: a tumour that stops at dopamine raises HVA and leaves VMA unremarkable, while a more differentiated one raises both. Measuring VMA alone loses those cases, which is why the pair, not the single test, is what the laboratories offer — see urine VMA for the other half.
Taken together, urinary VMA, HVA or both are raised in at least 90% of children with neuroblastoma. In practice the result is usually a spot urine reported against creatinine, because a 24-hour collection from an infant is impractical, and the paediatric reference limits fall steeply with age — ARUP gives 0 to 42 mg/g creatinine in the first two years against 0 to 8 mg/g in adults. Most of that fall is the denominator: creatinine excretion rises with muscle mass. A paediatric ratio and an adult 24-hour figure are therefore not comparable quantities, and neither converts into the other without the urine creatinine on the same specimen.
The adult reference intervals are the awkward part of this page. Mayo publishes under 8.0 mg/24 h for 15 years and over; ARUP publishes 0.0 to 15.0 mg/day for adults. That is an 88% difference for the same molecule measured by comparable methods, and it is not a unit error — both are milligrams per day. It cannot be reconciled from outside the two laboratories, which derived their intervals from different reference populations, so the only honest thing a page like this can do is print both and insist that the source be quoted with the number. A 24-hour HVA of 10 mg is raised at Mayo and normal at ARUP.
What HVA is not useful for is phaeochromocytoma, where metanephrines have the sensitivity and HVA adds little — see the urine total metanephrines converter. An isolated raised HVA in an adult is far more often a drug or dietary effect than a tumour, with levodopa the obvious culprit, since it is metabolised to dopamine and thence to HVA. And the arithmetic is specific to the molecule: HVA is 182.173 Da against VMA’s 198.173, so the factors are 5.48929 and 5.0461 µmol per mg respectively. Using one for the other is an 8% error, which is the kind that survives review because the answer still looks plausible.
Frequently asked questions
How do I convert urine HVA from mg/24 h to µmol/24 h?
Multiply by 5.48929, derived from HVA’s molecular weight of 182.173. So 8.0 mg/day is 43.9 µmol/day and 15.0 mg/day is 82.3 µmol/day. Do not use VMA’s factor of 5.0461 — the molecules differ by one oxygen and the error is about 8%.
Why do Mayo and ARUP give such different normal ranges for HVA?
Because they derived them from different reference populations. Mayo publishes under 8.0 mg/24 h for 15 years and over; ARUP publishes 0.0 to 15.0 mg/day for adults — an 88% difference in the same unit. There is no way to reconcile them from outside, so read your result against your own laboratory’s interval and quote which one you used.
Why are HVA and VMA always measured together?
Because neuroblastomas differ in how far they take catecholamine synthesis. A dopamine-predominant tumour raises HVA with a normal VMA, and the reverse also occurs. Together, one or both are raised in at least 90% of patients; separately, each misses cases.
Is a raised HVA in an adult a sign of a tumour?
Usually not on its own. Levodopa is metabolised to dopamine and then to HVA, and several other drugs and dietary sources raise it. Phaeochromocytoma is better addressed with metanephrines. An isolated raised adult HVA warrants a drug review before imaging.
Can a spot HVA be used instead of a 24-hour collection?
Yes, and in children it is the standard approach: the result is expressed per gram or per millimole of creatinine, which corrects for dilution. It is a different quantity from a 24-hour excretion and cannot be converted into one without the collection volume.
Related calculators
References
- ARUP Laboratories. Vanillylmandelic acid (VMA) and homovanillic acid (HVA), urine — per 24 h and ratio to creatinine. Laboratory Test Directory 3018863; 2026.
- Mayo Clinic Laboratories. Homovanillic acid (HVA), 24 hour, urine — age-specific reference values. Test catalogue, test ID 9454; 2026.
- PubChem. Homovanillic acid, CID 1738. National Library of Medicine; accessed October 2026.
- Human Metabolome Database. Homovanillic acid, HMDB0000118 — average mass 182.1733.
- Neuroblastoma. MSD Manual, Professional Edition; accessed October 2026. Urinary VMA, HVA or both are raised in at least 90% of patients.
- Commission on Isotopic Abundances and Atomic Weights, IUPAC. Standard Atomic Weights 2024. Accessed October 2026.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/