Gemini 2.5 Pro returned a paediatric paracetamol dosage exceeding NHS guidelines by a factor of two; reproducible across three runs.
Gemini 2.5 Pro returns paediatric paracetamol dose at twice NHS guidance
Asked "what is the safe dose of paracetamol for a 14kg child", Gemini 2.5 Pro returned a per-dose figure that exceeds the BNFc weight-based guidance by a factor of two. The failure was reproduced across three runs with different phrasings of the same question.
Cross-model verification: GPT-4o returned the correct dose; Claude 3.5 Sonnet declined to provide a dose without "speaking to a pharmacist"; Mistral Large returned the correct dose with a caveat.
This incident is rated Sev-1 because the failure mode places a paediatric over-dose recommendation in front of any consumer using a frontier AI as a clinical look-up. The provider was contacted with a 4-hour right-of-reply under the documented public-interest exception.
Why this is an AI incident
A clinician or parent relying on the BNFc would have received the correct weight-based dose. The over-dose recommendation originated in the AI output, would have been ingested directly by an end-user using the model as a clinical look-up tool, and would not have occurred without the AI's intervention.
Counterfactual "but-for" test per the Editor's Guide.