Phenylalanine (Phe) Test — Specimen and Method Not Specified

What is this test?

A phenylalanine test measures the amount of the amino acid phenylalanine in a sample, most commonly blood. The test slug does not clearly identify the specimen or testing method, so the laboratory report should be checked for those details.

Why might I need this test?

Phenylalanine is commonly measured during newborn screening because an elevated level can be associated with phenylketonuria, an inherited condition in which the body cannot properly process phenylalanine. It may also be used to monitor treatment or investigate symptoms of a metabolic disorder.

How is the test performed?

For a newborn screening test, a few drops of blood may be collected from a heel prick. Other testing may use a blood sample drawn from a vein. The laboratory analyzes the sample and reports the phenylalanine result, sometimes along with other screening markers.

How do I prepare for the test?

Newborn screening usually requires no special preparation beyond allowing the baby to receive regular feedings before the sample is collected. For other blood tests, follow the laboratory's instructions about fasting, feeding, and medication timing, as preparation may vary.