On previous occasions when I had donated blood I had noticed that if I consumed a lot of sugary foods afterwards it didn’t have the same effect as it usually did. Normally I would have difficulty getting to sleep, but not after donating blood. So for my most recent blood donation I checked by blood sugar before and then several times after my donation to see if the effect could be measured.

It turns out there really is a difference. After eating a few snacks at the clinic (some oreos and orange juice) I walked home (about 20 minutes). I ate two 100 gram bars of milk chocolate (containing 95 grams of sugar). On previous occasions eating 200 grams of milk chocolate had resulted in my blood glucose spiking to 10.3 mmol/L. On this occasion however, the rise in blood glucose was far lower, only going to 8.3 mmol/L, even though the actual sugar consumed was higher this time due to a difference in the chocolate (95 grams vs 80 grams of sugar).

Here’s the table showing the data.

And a table showing the maximum blood glucose readings with eating 200 grams of milk chocolate under different conditions.

It’s a pretty significant difference, specially considering that more sugar was consumed this time. The data confirm my earlier subjective evaluation. Here’s a chart showing the initial pre-donation reading and then the changes afterwards.