Medical necessity means those items or services considered to be reasonable and required to treat or diagnose an injury or illness or to improve functioning of a body part. In other words, the service/treatment needs to make sense when used with the diagnosis. It is unlikely that a provider will cover a knee x-ray if the patient was diagnosed with a headache.
There are 5 steps to establish medical necessity. You won't often need to go beyond the first one, but we all need help sometimes. Here is the process for getting assistance:
1. The diagnosis must justify the treatment/procedure/care/medication given
but if there is no guideline --->
2. Check the MCD (Medicare coverage database)
but if there is no guideline --->
3. Check the NCD (National coverage database)
but if there is no guideline --->
4. Check the LCD (Local coverage data)
but if there is no guideline --->
5. Check with the local MAC medicare administrative contractor - they may need to write one!
Note: Sometimes a condition is thought to be the cause of the individual's symptoms but testing discovers that it isn't. You will still need to code a Dx to justify the testing etc done. In these cases symptom coding and/or "suspected conditions ruled out" are your lifeline.