If given I am about to measure the effect of the extract on a 30 day basis, on which interval should I fast the mice and measure their blood glucose levels?
It will be good enough if you can measure it on 0,7th,14th,21st and 28th day. We got excellent results in our research. But you have to observe the physical condition of the mice daily for any hypo or hyper glyceamic effects.
If you are experimenting on hypoglycemic activity of a plant extract (trust you have pickedup the plant based on some earlier scientific ref.)...why fast the animal at any time ...it may give erroneous results away from true effect of plant extract. test blood sugar levels on normal conditions .However, in normal animals o,1,3,7,14,21 and 28 day observations may be good but if you are working with alloxan or streptozotocin diabetic animals the intervals should be more presise.
After 2 hours of heavy meals in comparison with a control group. If you noticed a sig. reduction, go ahead. If no change between groups, the extract is not work, dont waste your time!