How G6PD deficiency is inherited

A father passes his X chromosome to daughters and his Y chromosome to sons. A mother passes one of her X chromosomes to each child. This is why a family history can affect children differently, and why a relative may carry a G6PD gene change without having the same level of enzyme activity or symptoms.

The condition can cause red blood cells to break down after certain triggers. During an episode, signs may include jaundice, fatigue, breathlessness or [Dark Urine](/symptoms/dark-urine/). These signs require assessment; they do not show which family member passed on the gene.

Tell close relatives when G6PD deficiency is diagnosed, particularly before a child needs medicines or treatment for an infection. A clinician can decide who may benefit from a [Blood Test](/treatments/diagnostics-and-screening/blood-test/) and explain what the result can and cannot show. Keep the diagnosis in medical records and mention it during pregnancy and newborn care.

Seek urgent help for sudden severe tiredness, fainting, difficulty breathing, confusion, a very fast heartbeat, or dark urine with yellow eyes or skin. For a child, urgent review is needed if there is poor feeding, unusual sleepiness or [Pale Skin](/symptoms/pale-skin/). Tell the service that G6PD deficiency may be involved.

Ask which relatives should discuss testing, how results affect medicines, whether a genetic consultation is appropriate, and how to document the diagnosis for children.