Glucose-6-phosphate dehydrogenase (G6PD)

The Glucose-6-phosphate dehydrogenase blood test measures G6PD enzyme activity within red blood cells, helping identify G6PD deficiency.

The test assesses 1 red-cell enzyme marker: Glucose-6-phosphate dehydrogenase (G6PD).

G6PD is an enzyme involved in the pentose phosphate pathway.

Within red blood cells, this pathway generates protective reducing capacity that helps defend the cells against oxidative stress.

Red blood cells are particularly dependent on this mechanism because they lack many of the repair systems present in other cells.

In people with G6PD deficiency, red blood cells can become vulnerable to oxidative damage.

Exposure to certain medicines, infections, foods or chemicals can trigger haemolysis, where red blood cells break down faster than they can be replaced.

G6PD deficiency is an inherited X-linked condition.

It is more commonly clinically expressed in males, although females can also have clinically relevant deficiency depending on their genetic pattern.

The condition is more prevalent in people with ancestry from malaria-endemic regions, including parts of Africa, the Mediterranean, the Middle East and Asia.

Many people with G6PD deficiency remain completely well until exposed to a trigger.

Potential triggers include certain oxidant medicines, severe infection and fava beans in susceptible individuals.

Testing can be important before selected medicines are prescribed.

Timing also matters.

During or immediately after an acute haemolytic episode, the remaining circulating red cells can be enriched with younger cells that have relatively higher enzyme activity.

This can occasionally produce a falsely reassuring result.

Repeat testing may therefore be required after recovery where clinical suspicion remains high.

The specialist laboratory turnaround for G6PD enzyme testing is approximately 4 days after laboratory receipt.

This is a specialist red-cell enzyme assay.

The specimen undergoes enzyme analysis, quality-control procedures and result authorisation.

Turnaround begins when a suitable sample reaches the laboratory rather than necessarily from the exact time of collection.

A deficient screening result may occasionally require further quantitative or genetic investigation.

A result showing normal G6PD activity means the measured enzyme activity falls within the laboratory's expected range.

Where testing has been performed during or immediately after acute haemolysis, a normal result may occasionally be misleading because older deficient red cells can have been destroyed preferentially.

A repeat test after recovery may therefore be appropriate when clinical suspicion remains strong.

A reduced or deficient result supports G6PD deficiency.

The severity of enzyme reduction can vary according to the underlying genetic variant.

The practical importance of diagnosis is avoiding clinically relevant oxidative triggers.

A G6PD result does not by itself indicate whether haemolysis is happening at that particular moment.

During an acute episode, Full Blood Count, Haemoglobin, Bilirubin, Reticulocytes, LDH and Haptoglobin can provide complementary information about red-cell destruction.

Recent transfusion can also affect the result because donor red cells may have normal G6PD activity.

London Blood Tests provides private G6PD testing for people requiring assessment of this inherited red-cell enzyme.

The test costs £108 and assesses 1 specialist biomarker.

Results are expected approximately 4 days after laboratory receipt.

Correct timing is important because recent haemolysis or blood transfusion can affect interpretation.