The reason it's so bad is because dentists, doctors offices, hospitals and health insurance companies have also gone through this same massive consolidation.

CVS Health Corporation owns almost 10,000 drug stores and fills more than 20% of all US prescriptions. It also owns Aetna, the largest health insurance company in the US. It's the fourth largest US company by revenue. Another health insurance company is number five.

The largest health care operator in the US is HCA Healthcare which runs 187 hospitals, and has $60 billion in revenue.