Cholestanol Unit Converter
Cholestanol Unit Converter
Convert plasma cholestanol between mg/L, µg/mL, mg/dL and µmol/L. It is cholesterol with one double bond saturated, so its mass is cholesterol’s plus two hydrogens — and it is the marker for a treatable disease that is usually diagnosed late.
Cholestanol converter
mg/L ⇄ µmol/LPlasma cholestanol 6.0 mg/L — Mayo’s upper reference value
The conversion, and the two-hydrogen relation behind the mass
mg/L = µmol/L ÷ 2.57281
mg/L = µg/mL — the same quantity
mg/dL = mg/L ÷ 10
- 388.68
- the molar mass of cholestanol, C27H48O. The independent check is structural: cholestanol is cholesterol with the 5,6 double bond saturated, so its mass is cholesterol’s 386.65 plus two hydrogens, 388.67. The formula sum from standard atomic weights gives 388.68 and a chemical catalogue gives 388.67 — a 0.003% spread, where the conversion guard tolerates 0.5%
- mg/L, not mg/dL
- the sterol panel reports mg/L while the rest of the lipid profile reports mg/dL. A cholestanol of 6 mg/L is at the upper limit; read as 6 mg/dL it would be 60 mg/L, ten times the limit
- the ratio, not the absolute value
- most of the cerebrotendinous xanthomatosis literature uses the cholestanol-to-cholesterol ratio rather than cholestanol alone, because the absolute value tracks the total cholesterol it is carried with. This page converts the absolute value; the ratio is dimensionless and needs no conversion
Worked example
Plasma cholestanol 6.0 mg/L — Mayo's upper reference value
6.0 × 2.57281 = 15.4 µmol/L
= 6.0 µg/mL = 0.60 mg/dL
At Mayo's reference limit of 6.0 mg/L or less
Check the mass: cholesterol is 386.65 and cholestanol differs by two hydrogens, so 386.65 + 2.016 = 388.67 — within 0.003% of the 388.68 this page converts with, and a structural check that does not depend on any catalogue
Untreated cerebrotendinous xanthomatosis usually runs several times this figure, so a borderline value is far more likely to be cholestasis or high cholesterol absorption
Cholestanol in each unit, against Mayo’s limit
| mg/L (= µg/mL) | µmol/L | mg/dL |
|---|---|---|
| 2.0 | 5.1 | 0.20 |
| 4.0 | 10.3 | 0.40 |
| 6.0 | 15.4 | 0.60 |
| 12.0 | 30.9 | 1.20 |
| 24.0 | 61.7 | 2.40 |
| 40.0 | 102.9 | 4.00 |
Cholestanol against cholesterol — one molecule apart
| Cholesterol | Cholestanol | |
|---|---|---|
| Formula | C27H46O | C27H48O |
| Molar mass | 386.65 | 388.68 |
| Typical plasma concentration | about 1,500–2,000 mg/L | up to 6.0 mg/L |
| Reported in | mg/dL or mmol/L | mg/L or µmol/L |
| Raised in | many conditions | cerebrotendinous xanthomatosis; cholestasis |
The sterol that names a treatable disease
Cholestanol is cholesterol with the 5,6 double bond saturated — the same carbon skeleton, two more hydrogens. It is present in plasma at a few milligrams per litre, a few hundredths of a per cent of the cholesterol beside it, and under normal circumstances it is of no interest at all. It becomes interesting because of what makes it accumulate.
Cerebrotendinous xanthomatosis is a recessive defect of CYP27A1, the mitochondrial sterol 27-hydroxylase that performs an early step in bile acid synthesis. With the normal route blocked, intermediates are shunted down an alternative pathway that produces cholestanol, which accumulates in tissue — tendons, lens, and most consequentially the brain and spinal cord. The clinical course is recognisable in retrospect and rarely at the time: chronic diarrhoea in infancy, bilateral cataracts in childhood or adolescence, tendon xanthomas in early adulthood, then progressive spastic paraparesis, ataxia, peripheral neuropathy and cognitive decline.
The reason to measure it is that the treatment exists and the window closes. Chenodeoxycholic acid replacement suppresses the abnormal pathway and normalises cholestanol, and started early it prevents the neurological disease. Started late it arrests progression but does not recover lost function. Diagnosis is typically delayed by many years, usually because juvenile cataracts and unexplained diarrhoea are not connected until the neurology arrives — so a raised cholestanol in a patient with that history is a result to act on, with CYP27A1 sequencing to confirm.
Two cautions on reading the number. The unit is mg/L, not the mg/dL the rest of the lipid profile uses, and the limits on this panel are single figures, so a tenfold misreading is easy. And most of the literature uses the cholestanol-to-cholesterol ratio rather than the absolute value, because cholestanol travels with the cholesterol carrying it; the ratio is the better measure to follow on treatment. Reference intervals are method- and laboratory-dependent, and the interval printed on your own report takes precedence over any figure here.
Frequently asked questions
How do I convert cholestanol from mg/L to µmol/L?
Multiply by 2.57281, from cholestanol’s molar mass of 388.68 Da. So 6.0 mg/L — Mayo’s upper reference value — is 15.4 µmol/L. mg/L and µg/mL are numerically identical, and mg/dL is mg/L divided by ten.
What cholestanol level suggests cerebrotendinous xanthomatosis?
Mayo’s upper reference value is 6.0 mg/L, and untreated cerebrotendinous xanthomatosis typically runs several times that. A borderline elevation is more often cholestasis or a high cholesterol-absorption phenotype. The diagnosis is confirmed by CYP27A1 sequencing rather than by the sterol alone. Reference intervals are method- and laboratory-dependent, and the interval printed on your own report takes precedence over any figure here.
Why is cholestanol’s molecular weight so close to cholesterol’s?
Because it is the same molecule with one double bond saturated: C27H46O becomes C27H48O, so 386.65 becomes 388.67. That two-hydrogen relation is also the best available check on the conversion factor, since it does not depend on reading any catalogue correctly.
Should I use the absolute cholestanol or the ratio to cholesterol?
Both have a place. The absolute value in mg/L is what this page converts and what reference limits are published against. The cholestanol-to-cholesterol ratio is dimensionless, is less affected by the total cholesterol the sterol is carried with, and is what most of the literature and most treatment monitoring uses.
Does a normal cholestanol exclude the diagnosis?
Not in a patient already on treatment. Chenodeoxycholic acid normalises cholestanol, so a normal value on treatment is the expected result rather than evidence against the disease. In an untreated patient with the characteristic history a normal cholestanol makes it unlikely, but genetic testing settles it.
Related calculators
References
- Mayo Clinic Laboratories. Test ID: STER — Sterols, Plasma. Reference values in mg/L: sitosterol ≤15.0, campesterol ≤8.0, cholestanol ≤6.0, desmosterol ≤2.5, lathosterol ≤6.0. Accessed October 2026.
- ChemicalBook. CAS 80-97-7 — cholestanol (5α-cholestan-3β-ol, dihydrocholesterol). C27H48O, molecular weight 388.67.
- Commission on Isotopic Abundances and Atomic Weights (IUPAC). Standard Atomic Weights, 2021. Used to re-derive every molecular weight from its formula.
- Assay package inserts and the issuing laboratory’s own report — reference intervals are method-dependent and the local interval governs.
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/