Your doctor will likely do a thorough physical exam and ask detailed questions about symptoms and health. This may include examining the genital area and chest, performing tests to check reflexes, and assessing development and functioning.

The main tests used to diagnose Klinefelter syndrome are:

  • Hormone testing. Blood or urine samples can reveal abnormal hormone levels that are a sign of Klinefelter syndrome.
  • Chromosome analysis. Also called karyotype analysis, this test is used to confirm a diagnosis of Klinefelter syndrome. A blood sample is sent to the lab to check the shape and number of chromosomes.

A small percentage of males with Klinefelter syndrome are diagnosed before birth. This might be identified after a pregnant woman has a procedure to examine fetal cells drawn from the amniotic fluid (amniocentesis) or placenta for another reason, such as being older than age 35 or having a family history of genetic conditions.