Metabolic health
SCD-18 index (stearoyl-CoA desaturase)
Oleic to stearic acid ratio
Included in Complete.
Compare membershipsA rough guide to how stearic acid becomes oleic acid.
The SCD-18 index estimates the activity of stearoyl-CoA desaturase, the enzyme that converts stearic acid into oleic acid. It's usually calculated as oleic acid divided by stearic acid, though the exact formula can vary by lab.
Diet and enzyme activity both shape this index.
Oleic acid is one of the most plentiful fats in your blood. Some comes from foods such as olive oil, and some is made in the body from stearic acid.
Because both sources feed into the same number, this ratio is an imprecise estimate of enzyme activity. One study found it less consistent across different blood fractions than the SCD-16 index. It's mainly used in research.
Questions
What does my SCD-18 index mean?
There's no established clinical interpretation on its own. A higher index can reflect more oleic acid from food, more conversion of stearic acid, or both, so it's best read with your other fatty acids, metabolic markers, and eating habits.
Do I need to act on this result?
A single index result is rarely a reason to change anything by itself. A clinician will look for a broader pattern across your fatty acids and metabolic results before suggesting any change.