You have two options here I see:
1. Change brands
2. Change to white tea which is better in my opinion.
As for green tea extract, it may not be the safest option as there is a chance of it placing some undue stress on your pancreas. Drink tea the way it was meant to be drunk and that is not in extract form.
Also, green tea water should never be boiled but heated to a temperature of 80 degrees Celsius, whilst white tea's ideal water temp is best at 85. Boiling does damage the polyphenols and some of the other goodies that offset the harm caffeine may have on some individuals.
Fadi.