Chemical Pathology


7-dehydrocholesterol is used in the diagnosis of Smith-Lemli-Opitz syndrome. Blood and tissue of infants with Smith- Lemli-Opitz (SLO) syndrome contain reduced amounts of cholesterol and greatly increased concentrations of 7-dehydrocholesterol and of its isomer 8-dehydrocholesterol.

Features of this disease can include learning and behavioural problems. Physical abnormalities can be of varying severity; patients may have distinctive facial features, microcephaly, growth retardation, hypotonia, limb abnormalities, feeding difficulties and malformations of the heart, lungs, kidneys, gastrointestinal tract and genitalia.

Sample requirements

For adults, blood taken into a 5mL gold top gel tube (or rust top for the Acute Unit) and protected from light

5ml gold tube

For children, blood taken into a 3.5mL rust top tube and protected from light

3.5ml rust top tube

For neonates, blood taken into a 0.8ml minicollect tube and protected from light

Sample tube: pale green cap


  • Do not store. Send at ambient temperature to the laboratory on same day as sample collection.
  • 7-DHC is photosensitive, so blood samples must be protected from the light - wrap in foil or brown paper immediately after collection/labelling.

Required information

Relevant clinical details including details of clinical presentation.

Turnaround times

Samples are sent for analysis to the North Bristol NHS Trust with a result expected within 6 weeks.

Reference ranges

Plasma 7-dehydrocholesterol: less than 2.5 µmol/L

Further information

To learn more about 7-dehydrocholesterol visit National Metabolic Biochemistry Network or

Page last updated 20/04/2021