I agree you can't be insured against conditions you already know you have. But I think that means that at the moment you are diagnosed with the condition, your

I agree you can't be insured against conditions you already know you have. But I think that means that at the moment you are diagnosed with the condition, your current insurer should be liable for future costs that arise from that condition. Because your future expected healthcare costs, and hence also your future expected free-market-priced premiums, went up at that moment — that's a loss you incurred, and you should have been able to (choose to) insure against the risk of incurring that loss. The problem is that insurance products you can buy don't cover that risk (and people have to rely on other dodges to keep their premiums reasonable, like insurance pooling) — and that's market failure.