Plain version: renewability answers two questions: can the insurer drop the insured, and can it raise the price? Learn the five provisions as a ladder, from least to most protection for the insured: cancellable, optionally renewable, conditionally renewable, guaranteed renewable, noncancelable.
The bottom three rungs:
Cancellable: the insurer can end the policy during the term.
Optionally renewable: the insurer can refuse to renew for any reason. In California, a policy that reserves the right to refuse any renewal uses Form B of the grace period provision: the grace period is granted unless the insurer gave written notice of nonrenewal at least five days before the premium due date (Ins. Code §10350.3).
Conditionally renewable: the insurer can refuse to renew only for reasons stated in the policy, not because of one insured's health.
Guaranteed renewable (Ins. Code §10273): the insured can keep the policy in force by paying premiums on time until at least age 50 or, if the policy is issued after age 44, for at least five years. During that time the insurer cannot change any provision on its own, except premium rates for everyone in the same rating class.
Noncancelable (Ins. Code §10273.3): the right to renew is guaranteed, and the premium is also held at the amount set in the policy. It is the top rung. Exam trap: a locked premium means noncancelable; class-wide rate increases mean guaranteed renewable.
Individual health benefit plans in California are renewable at the individual's option, except for listed reasons (Ins. Code §10273.6): nonpayment after the individual is notified and billed and the grace period passes; fraud or intentional misrepresentation of material fact; or moving out of the service area when coverage ends uniformly regardless of health. A diagnosis or high claims is never a reason to refuse renewal.