OpenAI reports that GPT-5.5 Instant, released in May 2026, brings substantial improvements to health-related responses in ChatGPT, now available to all free users. The model is rated comparably to frontier Thinking models on the company’s most challenging health evaluations, including HealthBench and HealthBench Professional. These evaluations use realistic health conversations and physician-written rubrics to assess accuracy, safety, communication, context awareness, completeness, and appropriate escalation.

GPT-5.5 Instant shows improvements in recognizing when urgent care may be needed, asking for relevant context, explaining uncertainty, and making complex information easier to understand. In a separate comparison where physicians wrote responses to health conversations with unlimited time and internet access (but no AI), a panel of physicians rated GPT-5.5 Instant responses higher than both physician-written and older model responses across accuracy, communication, completeness, instruction following, and health decision helpfulness, based on 3,500 reviewed responses. GPT-5.5 Instant also had fewer failure modes, including fewer instances of not tailoring to local healthcare context, missing red flags or referral to care, or failing to seek additional context.

Production traffic monitoring shows the rate of responses with at least one flagged factuality issue in health has fallen by 71% in the last two months, based on billions of health messages per week. OpenAI attributes this progress to both advances in model capabilities and the work of a global network of more than 260 physicians across 60 countries, 49 languages, and 26 medical specialties. These physicians review example model responses, describe ideal behavior, and identify failure modes. To date, they have reviewed more than 700,000 example responses. Their feedback becomes rubrics and evaluation criteria used to measure model performance. The improvements are also relevant to OpenAI‘s broader healthcare tools, including ChatGPT for Clinicians and OpenAI for Healthcare.