In adults who are not pregnant, the reference range of alpha-fetoprotein is less than 6.0 nanograms per milliliter, states Mayo Clinic. Levels greater than 500 nanograms per milliliter are consistent with hepatocellular carcinoma, a type of liver cancer, and germ cell tumors of the ovaries and testes, according to MedicineNet.
High levels of alpha-fetoprotein are not diagnostic of malignancy. They are normal in pregnant women and neonates; levels as high as 100,000 nanograms per milliliter have been reported in newborns, notes Mayo Clinic. High levels also occur in people with benign liver disease, such as hepatitis or cirrhosis, and in people with ataxia-telangiectasia, a disorder of the immune and nervous system, explains Genetics Home Reference. The test is most useful as a means of following the progress of patients who are being treated for cancer. For example, high levels that fail to return to normal within one month of surgery to remove an alpha-fetoprotein-producing tumor suggests the presence of residual disease, reports Mayo Clinic.