The diagnosis of hyperlipoproteinemia Type III is also based on a combination of factors – symptoms, medical history and test results. Blood tests are used to identify elevated triglycerides, VLDL-cholesterol and blood sugar. These abnormal lipoproteins can be analyzed in the blood sample using a technique called electrophoresis, which separates components based on molecular size.

Other diagnostic tests can be used to monitor thyroid, liver and spleen function. If a patient has the characteristic symptoms of hyperlipoproteinemia Type III (high triglycerides, high VLDL-cholesterol, and xanthomas), a diagnosis can be confirmed by DNA testing of the APOE gene.

Nearly everyone affected by hyperlipoproteinemia Type III has two copies of the APOE e2 allele. However, not everyone with this genotype will suffer from the disorder, as other factors (genetic, environmental and hormonal) are also involved.