Modifier 25 should be appended to the office or other. outpatient service code to indicate that a significant, separately. identifiable E/M service was provided by the same physician. on the same day as the preventive medicine service.
The level of homocysteine in the blood can be measured with a simple blood test that is often, but not always, done after fasting. Homocysteine levels of 12 mmol/L are considered normal and levels below 10 mmol/L are considered desirable.
This finding suggests that methylmalonic acid and homocysteine levels can be early markers for tissue vitamin B12 deficiency, even before hematologic manifestations occur. Use of methylmalonic acid and homocysteine levels in the diagnosis of vitamin B12 deficiency has led to some surprising findings.