Health insurance is designed to help you pay for the cost of health care if you get sick or suffer an injury, but getting coverage can be difficult if you already have health problems. A health insurance carrier has traditionally been able to deny you coverage if you have a pre-existing health condition. However, that likely will change given the passage of the Affordable Care Act.

Cancer

Cancer can lead to long series of expensive treatments, which can end up being very costly for health insurance companies. As a result, many insurance companies have traditionally denied coverage for new customers who currently have cancer and need treatment.

Heart Disease

Heart disease describes a range of health problems that affect the ability of the heart to operate normally, such as constricted arteries and heart defects. If someone suffers from heart disease, they are more likely to suffer life-threatening health problems like heart attacks and strokes. This makes them unattractive customers to health insurance companies.

Pregnancy

Reasons for denying health care coverage are not limited to injuries and illness. The high cost of delivering a baby and providing care before and after birth makes it expensive for insurance companies to cover pregnant women. According to BlueCross BlueShield of Illinois, a woman who is currently pregnant can be denied coverage when applying for an individual insurance plan. However, pregnancy can't be considered a pre-existing condition for group health plans, which are plans you get through an employer.

Chronic Conditions

A health insurance company have traditionally been able to deny coverage for any chronic health condition that is likely to make a person expensive to insure. Examples of chronic health problems that can lead to a denial of coverage include diabetes, sleep apnea, mental disorders, multiple sclerosis and muscular dystrophy. Infections and other serious diseases like AIDS, HIV, cirrhosis and hepatitis can also lead to a denial of coverage.

The Affordable Care Act

The Affordable Care Act, a health reform law created in 2010, changes the rules for pre-existing conditions. Under the Act, health insurance companies generally cannot deny health insurance coverage for any pre-existing health condition starting in 2014. Certain plans created or purchased in 2010 or earlier are considered "grandfathered" and may still deny coverage for pre-existing conditions, but you are free to switch to a new plan to immediately get coverage for pre-existing conditions.