Sitosterol Unit Converter
Sitosterol Unit Converter
Convert plasma sitosterol between mg/L, µg/mL, mg/dL and µmol/L — and notice the unit before the number, because the sterol panel reports mg/L where the rest of the lipid profile reports mg/dL.
Sitosterol converter
mg/L ⇄ µmol/LPlasma sitosterol 15.0 mg/L — Mayo’s upper reference value
The conversion, and the unit trap in front of it
mg/L = µmol/L ÷ 2.41128
mg/L = µg/mL — the same quantity
mg/dL = mg/L ÷ 10
- 414.718
- the molar mass of beta-sitosterol, C29H50O. HMDB gives 414.718 and the formula sum from standard atomic weights gives 414.718 — the two agree exactly
- mg/L, not mg/dL
- the error this page is mostly for. Mayo’s sterol panel reports mg/L, while cholesterol, triglyceride and the rest of the lipid profile come in mg/dL. A sitosterol of 15 mg/L read as 15 mg/dL is tenfold wrong, and in the direction that invents a disease
- µg/mL
- numerically identical to mg/L, so a report in either means the same thing. Both appear in the sitosterolaemia literature
- read with campesterol
- the two plant sterols rise together in sitosterolaemia, and Mayo’s limit for campesterol is 8.0 mg/L on the same panel. Do not convert it with the factor above: campesterol is a different molecule with a different molar mass, so it needs its own
Worked example
Plasma sitosterol 15.0 mg/L — Mayo's upper reference value
15.0 × 2.41128 = 36.2 µmol/L
= 15.0 µg/mL = 1.50 mg/dL
At Mayo's reference limit of 15.0 mg/L or less
The trap: the same result misread as 15.0 mg/dL would be 150 mg/L, which is ten times the upper limit and in sitosterolaemia territory — so the unit on the report decides whether this number is normal or alarming
Sitosterol in each unit, against Mayo’s limit
| mg/L (= µg/mL) | µmol/L | mg/dL |
|---|---|---|
| 2.0 | 4.8 | 0.20 |
| 5.0 | 12.1 | 0.50 |
| 15.0 | 36.2 | 1.50 |
| 30.0 | 72.3 | 3.00 |
| 60.0 | 144.7 | 6.00 |
| 100.0 | 241.1 | 10.00 |
The plasma sterol panel, as Mayo reports it
| Sterol | Upper reference value (mg/L) | What a high value indicates |
|---|---|---|
| Sitosterol | 15.0 | plant sterol absorption; sitosterolaemia |
| Campesterol | 8.0 | plant sterol absorption; sitosterolaemia |
| Cholestanol | 6.0 | cerebrotendinous xanthomatosis |
| Lathosterol | 6.0 | increased cholesterol synthesis |
| Desmosterol | 2.5 | desmosterolosis; DHCR24 block |
A plant sterol that should not be in the blood
Sitosterol is the commonest plant sterol in the diet, structurally close enough to cholesterol that the gut absorbs it readily. Normally almost all of it is pumped straight back into the lumen by the ABCG5/ABCG8 heterodimer in the enterocyte, and whatever reaches the liver is excreted into bile by the same transporter. The result is that plant sterols make up a vanishing fraction of circulating sterol despite a substantial intake — which is why a plasma sitosterol is a clean readout of intestinal sterol absorption.
In sitosterolaemia, a recessive disorder of ABCG5 or ABCG8, that pump does not work. Plant sterols accumulate to many times the normal concentration, and the clinical picture is odd for a lipid disorder: tendon and tuberous xanthomas, premature coronary disease, and a haematological component — macrothrombocytopenia and haemolysis — caused by abnormal sterols in the red cell and platelet membranes. Total cholesterol may be normal or only modestly raised, so the diagnosis is routinely missed in a patient worked up as familial hypercholesterolaemia.
Making it matters because the treatment is different. Statins lower cholesterol synthesis and do little for an absorption defect; ezetimibe blocks the sterol absorption transporter and, with a low plant-sterol diet and a bile acid sequestrant, is what actually brings plant sterols down and resolves the xanthomas and the cytopenias.
The practical trap is the unit, not the chemistry. The plasma sterol panel reports mg/L while the rest of the lipid profile reports mg/dL, and all the limits on the panel are single or low double figures. A sitosterol of 15 mg/L is at the upper reference limit; the same figure read as mg/dL would be 150 mg/L, ten times the limit, and would look like the disease. Checking the unit on the report is a bigger part of interpreting this test than any arithmetic. 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 sitosterol from mg/L to µmol/L?
Multiply by 2.41128, from beta-sitosterol’s molar mass of 414.718 Da. So 15.0 mg/L — Mayo’s upper reference value — is 36.2 µmol/L. mg/L and µg/mL are numerically identical, and mg/dL is mg/L divided by ten.
What sitosterol level suggests sitosterolaemia?
Mayo’s upper reference value is 15.0 mg/L, and untreated sitosterolaemia usually runs many times that rather than marginally above it, with campesterol raised alongside. A borderline single plant sterol is more likely to be diet or cholestasis. Reference intervals are method- and laboratory-dependent, and the interval printed on your own report takes precedence over any figure here.
Why is the sterol panel in mg/L when cholesterol is in mg/dL?
Because plant sterols circulate at roughly a thousandth of the cholesterol concentration, so mg/dL figures would all be fractions. The consequence is the commonest error on this test: a result in mg/L read against a mg/dL expectation is wrong by a factor of ten, and in the direction that manufactures a diagnosis.
Does a statin lower sitosterol?
Not usefully. Statins inhibit cholesterol synthesis, and sitosterolaemia is a disorder of absorption and biliary excretion — some patients’ plant sterols even rise on a statin as absorption compensates. Ezetimibe, which blocks the intestinal sterol transporter, is the drug that works, with a low plant-sterol diet and sometimes a bile acid sequestrant.
Can plant sterol spreads raise it?
Yes, measurably, which is worth knowing before a mildly raised value is investigated. Sterol- and stanol-enriched foods are taken deliberately to lower LDL cholesterol, and in someone with normal ABCG5/ABCG8 they raise plasma plant sterols modestly. Ask about them before working up a borderline result.
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.
- Human Metabolome Database. HMDB0000852 — beta-sitosterol. C29H50O, average mass 414.718, CAS 83-46-5.
- 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/