As many predicted, Americans insured under the Affordable Care Act may not be able to keep their doctors--and even their hospitals.

A new study reveals that the average plans provided on the Obamacare health insurance exchanges offer 34 percent fewer providers than the average commercial plan offered outside the exchange.

The analysis from Avalere shows the disparity compared with commercial plans:  

• 42 percent fewer oncology and cardiology specialists
• 32 percent fewer mental health and primary care providers
• 24 percent fewer hospitals

Related: Top 10 Questions Consumers Ask About Obamacare

“Patients should evaluate a plan’s provider network when picking insurance on the exchange,” said Elizabeth Carpenter, vice president at Avalere. “Out-of-network care does not accrue toward out-of-pocket maximums, leaving consumers vulnerable to high costs if they seek care from a provider not included in their plan’s network.”

Patients need to evaluate a plan’s provider network when selecting insurance on the exchange, especially if they have a history of cancer or heart disease or require mental health services.

Limiting choice is one way for health exchanges to keep costs down, but ultimately patients bear the cost. “Plans continue to test new benefit designs in the exchange market,” said Dan Mendelson, CEO at Avalere. “Given the new requirements put in place by the ACA, network design is one way plans can drive value-based care and keep premiums low.”