A high-risk cover in health insurance refers to an insurance plan that offers coverage for high-risk ailments. Coverage for these ailments is usually not included under standard health insurance plans. Critical illnesses such as hypertension, heart disease and diabetes are usually considered high-risk ailments in health insurance. Some disabilities that may not be covered under regular health insurance plans, may be covered under a high-risk cover. However, these plans are usually expensive and offer only limited coverage for disability-related treatments.