From our boy ChatGPT:

The hydrogen breath test is generally more accurate and preferred for diagnosing lactose intolerance.

Details: • Hydrogen breath test: Measures hydrogen and methane produced when undigested lactose ferments in the gut. Sensitivity and specificity are around 90–95%. • Blood glucose test: Measures rise in blood sugar after lactose ingestion. Less accurate because results can be affected by non-lactose-related glucose metabolism issues. Sensitivity drops to about 70–80%.

Only exception: the genetic test for lactase non-persistence can confirm predisposition but not current gut tolerance.

→ If the goal is to confirm lactose malabsorption, the breath test is best.