• Health insurance has been a hot-button issue for Americans for decades. While most other industrialized countries offer universal, government-funded health care to its citizens, many Americans who do not have jobs that provide coverage and are not on a government plan like Medicare or Medicaid must buy their own coverage. However, 47 million Americans are uninsured, while another 25 million are underinsured, according to MSNBC. While many of these people simply cannot afford medical insurance, many others are not covered because health insurance companies deny their applications.
  
  

Pre-Existing Conditions

• Perhaps the biggest reason for a denial when applying for health insurance is a pre-existing condition. If you have one of a number of conditions, it is likely your application will be denied because the insurance company stands to lose money by covering you. According to the California Department of Insurance, each health insurance company has its own rules about whom they will turn down, but certain conditions will almost certainly mean a denial. These include AIDS, pregnancy, heart disease, multiple sclerosis, sleep apnea, serious mental disorders, cirrhosis and others. In 2010, President Barack Obama signed a health care reform law that will prevent insurance companies from rejecting applications based on pre-existing conditions. However, this provision of the law does not go into effect for adults until 2014.
  
  

History

• Health insurance companies will also be likely to decline your application if you have a history of engaging in "risky" behaviors. If you are a smoker or drink alcohol on a regular basis, it is likely your application for health insurance will be denied because you stand a greater risk for developing cancer or other diseases that will cost the company money. If you have a history of accidents or seeing a therapist, the insurance company may also deem you at risk for lapsing into a severe mental illness or even label you as accident-prone. This could apply if you suffer from something like joint sprains or strains. According to Daily Kos, you don't even have to be sick to be rejected, but if people closely related to you have suffered from numerous illnesses, it could stand as grounds for rejection.
  
  

Weight

• Another common reason for denial of health insurance is your height-to-weight ratio. If you are overweight or obese, you stand at a greater risk of developing health problems, something a health insurance company does not want to hear. According to the California Department of Insurance, some insurance companies use body-mass index to determine if they will accept a new client. If the person's BMI is 39 or over, the companies will automatically decline the application, and if it is over 30, there is a good chance the application will be rejected.