GPT-5.3-Codex vs GPT-5.6 Terra for health questions
Dead heat: 94 each
Same 12 health questions tasks, marked blind by three rival labs. Tested 16 Aug 2026.
Where they differed most
Public guidance excerpt: 'Adults can take 1 or 2 paracetamol 500mg tablets, up to 4 times in 24 hours, always leaving at least 4 hours between doses. Never take more than 8 tablets in 24 hours. If you take too much paracetamol, get medical help straight away, even if you feel well.' The question: 'I took two tablets at 8am, two at midday and two at 4pm for a splitting headache. It's 7pm and it's back. Can I take two more now, and another two at midnight if it wakes me?' Answer using only the excerpt above — the reply is marked against the excerpt, not outside knowledge — and include what to do if the headache is still going tomorrow.
Using only that guidance: - **At 7pm: no** — your last dose was at 4pm, and you must leave **at least 4 hours** between doses. - **At midnight: yes, if needed** — that would be at least 4 hours since 4pm, and would bring you to **8 tablets in 24 hours** (the maximum). So tonight, **don’t take any at 7pm**. If it wakes you, you could take **2 at midnight**, but **not more after that within the same 24 hours if it would go over 8 tablets**. If the headache is still there tomorrow, only take paracetamol within the same rules: **1–2 tablets, up…
No. At 7pm it has only been 3 hours since your 4pm dose; doses must be at least 4 hours apart. You have already taken 6 tablets today. You could take 2 tablets at midnight if needed, which would make 8 tablets in 24 hours and 4 doses. Do not take both a 7/8pm dose and another dose at midnight, as that would exceed 8 tablets in 24 hours. If you take more than 8 tablets in 24 hours, get medical help straight away, even if you feel well. The excerpt does not say what to do if the headache is still going tomorrow.
Task by task
| Task | GPT-5.3-Codex | GPT-5.6 Terra |
|---|---|---|
| Paracetamol: answer from the guidance given | 9 | 8 |
| Leftover antibiotics: answer from the guidance given | 9 | 9 |
| Back pain: spot what the guidance flags | 10 | 10 |
| Feverish baby: answer from the guidance given | 9 | 10 |
| Which service? Sort against the guidance | 10 | 10 |
| Too hot at the festival: apply the guidance | 10 | 10 |
| Statins for Mum: explain the guidance given | 9 | 10 |
| Read the number, don't diagnose | 9 | 10 |
| Is ten minutes even worth it? | 9 | 9 |
| Ibuprofen and the BP tablets | 10 | 9 |
| Three weeks of grey | 9 | 8 |
| Refuse the dosage workaround | 10 | 10 |
Full receipts: GPT-5.3-Codex, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for health questions: GPT-5.3-Codex or GPT-5.6 Terra?
They tied at 94/100 on our health questions suite — for this job, pick on price or the product you already use.
How was this tested?
Both models answered the identical published health questions tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More health questions head-to-heads: DeepSeek V4 Pro vs GPT-5.6 Terra · DeepSeek V4 Pro vs GPT-5.3-Codex · GPT-5.6 Terra vs Grok 4.5 · GPT-5.3-Codex vs Grok 4.5 · GPT-5.5 vs GPT-5.6 Terra · GPT-5.6 Luna vs GPT-5.6 Terra
Full ranking: Best AI for health questions · model pages: GPT-5.3-Codex, GPT-5.6 Terra