An insurer can only price a risk it can predict. An ideally insurable risk has six features.
The loss is due to chance: accidental, not intentional or planned, and not certain to happen. A cosmetic procedure the applicant has already scheduled fails this test.
The loss is definite and measurable in money.
The loss is statistically predictable.
The loss is not catastrophic: one event must not be able to bankrupt the insurer.
There is a large number of similar exposure units, so the law of large numbers can work.
Coverage is not mandatory for the insurer: the insurer may choose which applicants to accept.
The premium must also make economic sense compared with the loss. Small, routine costs, such as a monthly vitamin purchase, are close to certain, and once the insurer adds its expenses the premium would cost about as much as the item itself.
California's insurable events rule (Ins. Code §250): any contingent or unknown event, whether past or future, that may damage a person who has an insurable interest, or create a liability against that person, may be insured against, subject to the Code. A past event qualifies only while it is still unknown. One event is barred outright: a lottery or its outcome cannot be insured against (§251).