As a Vermonter, I have to ask - does the locale have anything to do with the low Vitamin D levels, any more than most of the rest of the northern United States?
devboone has previously said that less than 3000 IU per day should be safe, but again this should be determined with the help of a physician, not self-selected. She said she has definitely seen toxicity in some of her patients with doses of over 5000 IU per day.
Thank you very much for the straight answer. I'd prefer not to poison myself via Vitamin D! I worry with COVID-19 other people are going to be overcompensating as well.
The easiest solution is just to be stable at a level of supplementation for a few weeks (even zero), then get a test. They're like $40 for the blood test, and then you can tell if you're in the normal range, high or low.
Not all sunlight exposure works though. It needs to have enough UV-B in it. And that’s dictated by the time of year, the location, and the time of day. In some places, you may only get an hour or so of the right kind of rays.
Latitude, local geography and weather will all play a role in how much sunlight you get. If you're living in a valley you can have much shorter days than your latitude would suggest. And if the weather is shitty enough to keep you inside much of the year that will obviously have an impact.