Can my dad do this?

Can my dad claim me as a dependent on his tax return paperwork? I’m 23 years old and I haven’t been a full time college student at all. I have read online that if that’s the case then he can’t claim me. I keep telling him this but he insists I am a dependent. I think he’s trying to make me lie. He says I won’t be able to be covered by his health insurance policy if I claim myself. Is this true? I don’t mind paying for my own health insurance.