How would I get health insurance (21; living with grandparents)?

Since you have Crohn's you won't qualify for any insurance at this time in most states.

However, starting October 1 you'll be able to sign up for your own insurance through the ACA which will be effective January 1, 2014. If you are low income you might even qualify for a subsidy which would help pay the premium and possibly a cost-share reduction to help pay the deductible and co-pays.

You'll want to speak with an agent in your area for more assistance.

If your grandparents are your legal guardians, and they have private health insurance, you can be on their policy until you are 26. You can go to any doctor at any number of out-patient clinics without insurance but of course you pay a fee. Medical schools, hospitals, the county, all have out-patient cllinics which charge a small fee or use a sliding scale. There are also community clinics which cost about half of a private doctor. If you have a problem, ask for a generic prescription and get it filled at Walmart or Costco cheaper. You are old enough to buy insurance so October 1 go online and find pre-existing health insurance from your state's exchange if you have a condition.

First the bad news: in most states it’s still possible to be declined coverage based on your medical history. If you have Crohn’s disease, you’re application for health insurance coverage will likely be declined. The best way to get coverage with a pre-existing condition is through an employer-sponsored plan.

The good news is that this is all about to change in January 2014. As of January 1, you can no longer be declined for health insurance based on your medical history. And depending on your income, you may be eligible for government subsidies to help you afford coverage.

Open enrollment for reformed 2014 health insurance plans will begin in October and run through March 2014. You’ll be able to shop through licensed agents online or in your area, or else through your state’s health insurance exchange.

Good luck.

Same way you get car insurance.

You're right, you can't be added to your grandparents - but you can try to buy an individual policy. Unfortunately, unless your state's high risk health pool is active, both anxiety and Crohn's are normally automatic denials - so it's likely that neither of those things would be covered.

If you already need to see a doctor, and you don't already have insurance, then you need to pay the doctor, with money, and only with money, without using insurance. Currently (2013), you can't use insurance for something that you already needed before you had insurance (this changes in 2014). For something that you already needed when you did not have insurance, you need to use only money, and no insurance, or wait until 2014.

Call a health insurance broker and they will guide you.