Does sunlight lower your BG?

I have insulin-dependent diabetes. I live in a warm climate.

I have found - first as a result of unexplained hypoglycemic episodes, and then by trial and error - that exposing myself to sunlight - has a rather immediate effect on my BG. About 1/2 hour in direct sunlight can lower the BG by about 30 mg/dll. Sometimes even more dramatically.

Has anyone else noticed this?

I googled the topic and only find the opposite, like 'sunburn can raise BG', and some discussions about Vitamin D lowering BG (but that is a longer-term effect, not immediate as I noticed with the sun).

If anyone would like to participate in a little 'ad-hoc' experiment, try it out -- sit in the sun for 1/2 hour or so, making sure to expose arms, face, legs, to direct sunlight. And measure before-after BG. The lowering effect might take place only a few hours later.

Let's see if together we can learn something new!
Report your results here.


I usually experience something similar when it's very hot outside, but my bg drops in response to severe temperature, not so much to sunlight on its own...

I've noticed that since I was a teenager, that my sugars tend to drop while I am out in the heat and sun. It doesn't seem to matter whether I was just lying outside tanning or outside doing some work.

Thanks Melody and Terrie for your input. I am wondering myself if its the sunlight or the heat. Someone told me to try an indoor sauna...

I believe that being warmed out in the sunlight increases circulation and increases insulin absorption. The same reason we are advised to be careful around hot tubs. I've also noticed the blood sugar lowering, but no experiments, just my theory.

I think it has been well established through many discussions on this DOC and others that we need less insulin during the summer, I'm sure a few will say the opposite, but an over whelming majority will say they turn down their basal every spring and increase it every fall, even if only buy a small amount. I think it's temperature related and not caused by the acute radiation from the sun.

I'm not allowed to spend time in the sun but a extended temperature increase will force me to lower my basal. I own a manufacturing company and it is over a 100F during the summer in parts of the plant and it always drives my BG down.