Non-Esterified Fatty Acids Unit Converter
Non-Esterified Fatty Acids Unit Converter
Convert NEFA — free fatty acids — between mmol/L, µmol/L, mg/dL and mg/L, with the oleic-acid convention the molar figure actually rests on, and why mEq/L and mmol/L are the same number here.
NEFA converter
mmol/L ⇄ mg/dLNEFA 0.45 mmol/L in a fasting adult, serum separated within the hour
The conversion, and the convention inside it
mg/dL = mmol/L × 28.2461
µmol/L = mmol/L × 1,000
mEq/L = mmol/L — the same number
- 282.461
- the molar mass of OLEIC ACID, C18H34O2, not of any single substance in the sample. Serum NEFA are a mixture — palmitic, stearic, oleic, linoleic — with no common molar mass, and a molar figure is legitimate only because the assay is calibrated against oleic acid: Fujifilm Wako’s NEFA standard is oleic acid at 1 mEq/L, stated as equivalent to 1 mmol. So mmol/L here means oleic-acid-equivalent millimoles
- mEq/L = mmol/L
- because a fatty acid carries exactly one carboxyl group, so one millimole is one milliequivalent. This is a valency argument and not an approximation, and it is why the older literature’s mEq/L figures can be read directly as mmol/L
- the same shape as triglyceride
- the triglyceride converter on this site converts with triolein’s mass for the same reason: a mixture reported in molar units needs a named convention, and the convention is whatever the assay was calibrated with
Worked example
NEFA 0.45 mmol/L in a fasting adult, serum separated within the hour
0.45 ÷ 0.0354031 = 12.71 mg/dL
= 127.1 mg/L = 450 µmol/L = 0.45 mEq/L
Inside Mayo's interval of 0.00–0.72 mmol/L for adults, which in mass units is 0.00–20.34 mg/dL
Check: 1 mmol/L of oleic-acid-equivalent NEFA is 28.2461 mg/dL, which is just the molar mass divided by ten — and Wako's own standard is 1 mEq/L of oleic acid called 1 mmol, so the convention and the arithmetic agree
Had the sample sat unseparated, continuing lipolysis in the tube would have raised this figure without anything having changed in the patient
NEFA across the range, in every unit in use
| mmol/L (= mEq/L) | µmol/L | mg/dL | mg/L |
|---|---|---|---|
| 0.10 | 100 | 2.82 | 28.2 |
| 0.30 | 300 | 8.47 | 84.7 |
| 0.45 | 450 | 12.71 | 127.1 |
| 0.72 | 720 | 20.34 | 203.4 |
| 1.00 | 1,000 | 28.25 | 282.5 |
| 1.50 | 1,500 | 42.37 | 423.7 |
What moves a NEFA result, and by roughly how much
| Cause | Direction | Note |
|---|---|---|
| Delay in separating serum from cells | up | pre-analytical; lipolysis continues in the tube |
| Heparin, including a flushed line | up | releases lipoprotein lipase; can double the result |
| Prolonged fasting, stress, catecholamines | up | physiological lipolysis |
| Insulin, or a recent meal | down | insulin is the main antilipolytic signal |
| Adipose insulin resistance | up for a given insulin | the reason NEFA are measured with insulin, as Adipo-IR |
The most fragile number on a lipid panel
Non-esterified fatty acids — free fatty acids, NEFA, FFA — are the fatty acids circulating bound to albumin rather than packaged into triglyceride. They come from lipolysis in adipose tissue, and because insulin is the dominant brake on that lipolysis, the NEFA concentration at a given insulin level is a direct readout of how insulin-sensitive the fat is. That is the main reason the test is ordered: fasting NEFA multiplied by fasting insulin is the adipose insulin resistance index, and it sees something the standard indices built on glucose and insulin do not.
The molar unit needs a word of explanation, because a mixture has no molar mass. Serum NEFA are palmitic, stearic, oleic and linoleic acids in proportions that vary between people and within a person, with masses from 256 to 284 Da. A mmol/L figure is nevertheless legitimate, because the assay is calibrated against oleic acid: the standard solution is oleic acid, and the millimolar result is oleic-acid-equivalent. That is the same kind of convention the triglyceride assay uses with triolein, and naming it is what stops the mass conversion looking more exact than it is. A sample weighted towards palmitic acid carries about 9% less mass for the same molar figure.
The milliequivalent form needs no convention at all. A fatty acid has one carboxyl group, so a millimole is a milliequivalent, and the older literature’s mEq/L values are the same numbers as today’s mmol/L.
What really decides the interpretation is neither unit. NEFA turn over in minutes, rise with fasting, stress and catecholamines, and keep rising in the tube after the sample is drawn, because lipase in the specimen carries on hydrolysing triglyceride until the serum is separated. Heparin makes it worse by releasing lipoprotein lipase into the circulation, and a heparinised line is enough. A raised NEFA should be checked against how the sample was taken before it is checked against the patient. 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 NEFA from mmol/L to mg/dL?
Multiply by 28.2461, which is oleic acid’s molar mass divided by ten. So 0.45 mmol/L is 12.71 mg/dL and 0.72 mmol/L — the top of Mayo’s adult interval — is 20.34 mg/dL. The mass figure is oleic-acid-equivalent, because that is what the assay is calibrated against.
Are mEq/L and mmol/L the same for free fatty acids?
Yes, exactly. A fatty acid carries one carboxyl group, so one millimole is one milliequivalent. Fujifilm Wako’s NEFA standard is labelled as oleic acid at 1 mEq/L and described as equivalent to 1 mmol, which is the same statement from the manufacturer. So a historical result in mEq/L needs no arithmetic.
Why does NEFA need a molecular weight convention at all?
Because it is a mixture. Palmitic acid is 256.4 Da, stearic 284.5, oleic 282.5, linoleic 280.5, and the proportions vary, so there is no single grams per mole. The convention is the assay calibrant, oleic acid at 282.461 Da, and the resulting mmol/L is oleic-acid-equivalent rather than a true count of molecules.
What is a normal free fatty acid level?
Mayo gives 0.00 to 0.72 mmol/L for adults 18 and over, which is 0.00 to 20.34 mg/dL. The interval is wide because the analyte moves so quickly with fasting state and stress. Reference intervals are method- and laboratory-dependent, and the interval printed on your own report takes precedence over any figure here.
Why can a NEFA result be falsely high?
Two reasons, both common. Lipase in the specimen keeps hydrolysing triglyceride until the serum is separated, so a delay raises the result. And heparin — including a flush from a heparinised line — releases lipoprotein lipase into the blood and can double it. Both are pre-analytical and neither is correctable after the fact.
Related calculators
References
- Mayo Clinic Laboratories. Free Fatty Acids, Total, Serum. Reference value 0.00–0.72 mmol/L for 18 years and over. Accessed October 2026.
- Fujifilm Wako. LabAssay NEFA (W01S10LABNEFA-M1) — ACS-ACOD method; standard solution is oleic acid at 1 mEq/L, equivalent to 1 mmol. Accessed October 2026.
- Human Metabolome Database. HMDB0000207 — oleic acid. C18H34O2, average mass 282.4614, CAS 112-80-1.
- 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/