G6PD deficiency is included on newborn screening panels in several countries, but it is not on the federal Recommended Uniform Screening Panel (RUSP) in the United States. That means most U.S. states do not screen for it at birth. Whether your baby was tested depends entirely on where they were born.
Where G6PD Screening Is Standard
Countries with high rates of G6PD deficiency have built universal newborn screening into their healthcare systems. Greece, the Philippines, Israel, India, Singapore, Saudi Arabia, and the Italian island of Sardinia all screen newborns routinely. In several of these regions, universal screening has led to measurable drops in kernicterus (a type of severe brain damage caused by extremely high bilirubin) and dangerous reactions to fava beans.
In the United States, the picture is different. The RUSP, which guides state screening programs, includes conditions like sickle cell disease and other hemoglobin disorders but does not include G6PD deficiency as a core or secondary condition. A small number of U.S. states and territories have added G6PD screening on their own, including Pennsylvania and the District of Columbia. If you’re unsure whether your state screens for it, your pediatrician’s office or your state’s newborn screening program can tell you.
Why It Matters for Newborns
G6PD deficiency is the most common enzyme deficiency in the world, affecting hundreds of millions of people. Most adults with the condition live normal lives and only run into trouble when exposed to specific triggers. But the newborn period is uniquely risky. Babies with G6PD deficiency are far more likely to develop severe jaundice in the first week of life, with bilirubin levels that can climb above 20 mg/dL, peaking around days three to five.
That level of jaundice sometimes requires aggressive treatment. In one study, 31.5% of G6PD-deficient newborns needed an exchange transfusion (a procedure that replaces the baby’s blood to rapidly lower bilirubin), compared to just 4.6% of babies with normal enzyme levels. Without early identification, these infants can progress to kernicterus before anyone realizes what’s driving the jaundice. This is the core argument for screening: catching these babies before symptoms escalate.
How the Test Works
When G6PD screening is performed, it uses the same heel-prick blood spot collected for all other newborn screening tests. The lab measures how much G6PD enzyme activity is present in the blood sample. The most common method is a quantitative assay that tracks how quickly the enzyme produces a specific molecule (NADPH), measured by how it absorbs ultraviolet light. Higher enzyme activity means more production, which means the baby’s red blood cells can protect themselves normally.
Newborns naturally have higher G6PD activity than adults. The normal reference range for a newborn is roughly 10 to 15 U/g Hb, compared to about 7 to 12 U/g Hb in adults. Labs set a cutoff value below which a baby is flagged as deficient. That cutoff varies by institution but commonly falls somewhere between 5.7 and 8 U/g Hb. Using the lower adult cutoff catches the most severely deficient babies but misses some, particularly girls. Using a higher, newborn-specific cutoff identifies more cases overall.
The Problem With Detecting Female Carriers
G6PD deficiency is X-linked, meaning boys who inherit the gene variant are fully affected while girls can be carriers with one normal copy and one affected copy. This creates a screening challenge. A female carrier’s red blood cells are a mosaic: some produce normal enzyme levels, others don’t. Her overall enzyme activity can land anywhere from clearly deficient to completely normal, depending on how the X chromosomes were randomly inactivated during development.
Research from a large screening program in Guangxi, China illustrates the difficulty. When labs used a cutoff designed to catch deficient males, a considerable proportion of heterozygous females were missed entirely. Adjusting the cutoff upward improved sensitivity for female carriers to around 97.5%, but at the cost of flagging more healthy babies. About one-third of confirmed female carriers in that study had enzyme activity levels that appeared normal on standard testing. These girls can still experience hemolytic episodes when exposed to triggers, which is why a “normal” screening result in a girl with a family history of G6PD deficiency doesn’t fully rule out carrier status.
What Happens After a Positive Screen
If your baby’s screening result comes back out of range, your pediatrician will contact you to arrange follow-up testing. This typically includes a confirmatory blood test measuring G6PD enzyme activity more precisely, and sometimes genetic testing to identify the specific variant. False positives for G6PD deficiency are rare, so an abnormal result usually means the baby does have the condition.
There is one important exception: if your baby received a red blood cell transfusion before the screening sample was collected, the results will be inaccurate. The transfused blood contains normal G6PD levels from the donor, which can mask a deficiency. Similarly, testing during or right after a hemolytic episode (when the most vulnerable red blood cells have already been destroyed) can produce a falsely normal reading. In either case, a repeat quantitative test is needed once the situation has stabilized.
For babies confirmed to have G6PD deficiency, the immediate concern is monitoring for jaundice. Long term, management centers on avoiding known triggers: fava beans, certain medications (particularly some antibiotics and antimalarials), and naphthalene (found in mothballs). Infections can also trigger hemolytic episodes, so prompt treatment of fevers and illness matters. Most children with G6PD deficiency thrive with these precautions in place.
If Your State Doesn’t Screen
If you live in a state that doesn’t include G6PD on its newborn panel, you can request testing separately. This is especially worth considering if your family has roots in sub-Saharan Africa, the Mediterranean, the Middle East, or Southeast Asia, where prevalence is highest. A simple blood test at your pediatrician’s office can measure enzyme activity. Knowing your baby’s G6PD status before they encounter a trigger is far better than discovering it during a crisis.