Healthcare is becoming evermore expensive in the US with every passing day. Insurance companies have jacked up their premiums for life-saving drugs.

They are rapidly adopting a new pricing system for very expensive drugs, asking patients to pay hundreds and even thousands of dollars for prescriptions for medications that may save their lives or slow the progress of serious diseases.

With the new pricing system, insurers abandoned the traditional arrangement that has patients pay a fixed amount, like $10, $20 or $30 for a prescription, no matter what the drug’s actual cost. Instead, they are charging patients a percentage of the cost of certain high-priced drugs, usually 20 to 33 percent, which can amount to thousands of dollars a month.

The system means that the burden of expensive health care can now affect insured people, too.

No one knows how many patients are affected, but hundreds of drugs are priced this new way. They are used to treat diseases that may be fairly common, including multiple sclerosis, rheumatoid arthritis, hemophilia, hepatitis C and some cancers. There are no cheaper equivalents for these drugs, so patients are forced to pay the price or do without, says Gina Kolata, writing in the New York Times.

Insurers say the new system keeps everyone’s premiums down at a time when some of the most innovative and promising new treatments for conditions like cancer and rheumatoid arthritis and multiple sclerosis can cost $100,000 and more a year.