Which meter is it?
For the One Touch meters, a reading of "High" means a blood glucose level of over 600 which is considered a medical emergency.
Did he test more than once? Did he also perform a control test (with the control solution) to make sure the meter is functioning correctly? Double check to make sure the code on the strip container matches the code on the meter (if the meter requires one)?
There are quite a few things you can do to ensure that the reading is accurate before panicking.
If it does turn out that he's consistently getting the "High" as a reading after doing the above and re-testing a couple of times, you should insist he contact his doctor immediately.