You should not have a problem getting health insurance through an employer when you have bad credit, but this can vary from company to company. If you are attempting to get a private health insurance policy, you may have to agree to let them do a credit check in order to have a chance at being approved for coverage. Some companies want to do credit checks on applicants to see if they have a history of paying their debts. This allows them to be able to find out if you might have trouble paying your premiums. Credit reports also give them an opportunity to see your debt to income ratio (if you have supplied them with your income information), which can indicate if you can afford to pay your premium payments.
Companies want to know if you will make your payments, and they often use credit checks to predict if potential customers will pay their bills on time. Credit checks are becoming increasingly popular amongst insurance companies.