I'd use the 5,000, not the 2,000. Anytime someone walks past me with a virus, I take 50,000 iu for a few days. Never had a problem. (that's TEN 5,000 iu pills). I don't get sick much, anymore. I don't take 50,000 iu for more than 1-2 weeks, though. I've heard of doctors prescribing it, that way. I knew a woman who had sores all over her body from colitis. Her doctor told her to take 50,000 iu D3 a day, for 14 days. She didn't have any money and never got her prescription filled, so I gave her enough of my over-the-counter to take it. Her sores cleared up, like a miracle.
As far as I know, you can't really overdose with the D3. If you do, you'll probably notice the nausea and vomiting. You would need to take 50,000 iu every day for several months in order to get to that point. I know lots of people who take high doses of it, up to 50,000 iu, and have never overdosed, including myself.
So, if you want a good experiment, take 50,000 iu every day for 1-2 weeks, and then cut back to about 5,000 - 10,000 iu a day, which is what most folks that I know take.
I also suggest, for pain, a little MSM powder in whatever you drink, every day, about three capsules of fish oil a day, and a warm glass of Natural Calm magnesium supplement every night, along with a Malic Acid supplement. And epsom salt bath. Everyone in my house is now hooked on the Natural Calm, from my fourteen year old daughter (she mixes in sugar and ice to the lemon variety and drinks it like lemonaid) to my husband who is about to retire. It's indispensible to my seventeen year old daughter who has fibro and CFS. There are also forms of it with fruit flavors and stevia, but I like the original lemon fizzy version.