Familial hypercholesterolaemia (FH) is diagnosed when total cholesterol (TC) is greater than the age- and relationship-specific cut-off.

Age (years)	First-degree relative with FH	Second-degree relative with FH	Third-degree relative with FH	General population
<20	>220 mg/dL (5.7 mmol/L)	>230 mg/dL (5.9 mmol/L)	>240 mg/dL (6.2 mmol/L)	>270 mg/dL (7.0 mmol/L)
20–29	>240 mg/dL (6.2 mmol/L)	>250 mg/dL (6.5 mmol/L)	>260 mg/dL (6.7 mmol/L)	>290 mg/dL (7.5 mmol/L)
30–39	>270 mg/dL (7.0 mmol/L)	>280 mg/dL (7.2 mmol/L)	>290 mg/dL (7.5 mmol/L)	>340 mg/dL (8.8 mmol/L)
≥40	>290 mg/dL (7.5 mmol/L)	>300 mg/dL (7.8 mmol/L)	>310 mg/dL (8.0 mmol/L)	>360 mg/dL (9.3 mmol/L)

Use the row for the patient's age and the column for the closest relative with confirmed FH. If there is no confirmed FH in the family, use the general-population cut-off.

US (MEDPED) Diagnostic Criteria for Familial Hypercholesterolaemia (FH)