Health insurance denial & claim adjustment codes

What health insurance denial code 55 means on your EOB

The plan classified your treatment as experimental. These denials hinge on which clinical evidence the plan reviewed and whether its own policy is current.

What usually causes it

• The plan's medical policy predates newer evidence.
• The treatment is standard for your condition but not for the coded indication.
• FDA status and plan coverage status are not the same thing and the plan may have conflated them.

The documents that decide it

• The plan's medical policy with its revision date.
• Published guidelines from the relevant specialty society.
• Your provider's rationale tying the evidence to your case.

What to do next

Experimental denials usually qualify for external review, which is decided by an independent reviewer rather than the plan. That is often the faster path.

This page explains what a code means. It is information, not advice — it does not tell you whether your specific claim should have been paid, and it is not legal, medical, or insurance advice. Your plan documents and your denial notice govern your situation.