How to say "I have a headache" in Chinese

This is a simple topic-comment structure: 我 (I) is the topic, and 头疼 (headache) is the comment. There's no verb 'to have' in Chinese; the state is directly stated. 头 means head, 疼 means pain.

Use this when describing your symptom to a doctor or pharmacist. It's straightforward and appropriate in any register. To be more specific, you can add 很 (hěn) before 疼 to say 我头很疼 (wǒ tóu hěn téng) meaning "my head hurts a lot." Don't say 我有头疼 (wǒ yǒu tóuténg) – that's a common mistake; Chinese uses the topic-comment structure instead.