While approving MiniMed Inc.'s Continuous Glucose Monitoring System, which can take up to 288 measurements every 24 hours, the panel said more study was needed on how it works in some types of diabetics and some ethnic groups.The Food and Drug Administration usually follows the advice of its panels.

Before the panel vote, MiniMed shares closed $3 lower on Nasdaq at $85.25A sensor the size of a coin is inserted just under the abdominal skin. When the body's fluids pass over the sensor, an electrochemical reaction occurs. The signal, captured by a pager-like recording device connected to the sensor, is translated into a measure of blood sugar levels.

Patients continue to carry out finger-prick blood tests several times a day and enter their own results into the recording device,which they wear for up to three days at a time.

The data is downloaded into a computer that plots exactly when blood sugar spikes up or down. That information enables physicians to give their patients better advice on when to take an insulin shot or otherwise adjust medication.

To demonstrate the success of the system, MiniMed compared its results with finger-prick measures.