A reader named Tim G commented:
Blood tests last year  showed I had low Vitamin D levels so I was put on a 50,000 IU once/week regimen for 3 months using a prescription D2 (ergocalciferol). A recheck after 3 months showed my level had hardly changed. A search of PubMed showed conflicting views on using the D2 form. So for the next 3 months I used ProHealth D3 Extreme 50,000 IU (via Amazon.com) instead of another D2 scrip my doc had given me. I always took the D2 or D3 in the morning (just lucky happenstance.)
The second recheck, after the second 3 mo., showed my Vitamin D level was normal. I hadn’t put it all together until seeing this post, but when using the D3 I had the same effect [as what is described in this post] — when I got tired, I got *really* tired right at bedtime, and slept like a rock.
Even though it has been less than a month since stopping the weekly dose, I have noticed my sleep degrading somewhat, and lately not even being tired when I should.
I asked for details:
Tell me about yourself.
I’m a 50 year old reasonably healthy guy who is a lifetime Massachusetts resident. I’m in the IT profession (managing computer systems, programming and such). So I am someone who 1) lives at a higher latitude, 2) during the day garners minimal Vitamin D from the glow of LCD displays and fluorescent lights, and also 3) generally dislikes the heat of summer and burns easily.
Why did you take D3 once/week rather than once/day?
My intent was to mimic the original doctor’s prescription of a single 50K/wk dose, while substituting D3 for the prescribed D2. At the time, I had no good reason to change to a daily schedule, although it intuitively struck me as odd to take a single large dose rather than smaller, more evenly distributed doses.
What time in the morning did you take it? What time do you get up in the morning?
I get up around 6-6:30 am. I would take the D3 around 6:15-6:45 am.
Why did your doctor prescribe D2 rather than D3?
I think it was simply rote procedure and cost. When I asked him after my first 3 months on D2, he said that the prescription D2 was cheaper than the prescription D3, and that he had seen the D2 usually work quite well to bring up Vitamin D levels, although it did sometimes take multiple 3-month courses to achieve normal levels. He seemed unaware of the literature criticizing the use of D2 as a supplement.
You write: “When using the D3 I had the same effect of when I got tired, I got *really* tired right at bedtime, and slept like a rock” What was it like when you were taking the D2? What was your sleep like before you started the D2?
To the best of my recollection I did not have a similar response when taking D2. However, since this was not something I intentionally tracked, I may be mistaken.
Before taking D2 or D3 I thought I slept reasonably well. However, in retrospect, I would awake a few times during the night, take longer to fall asleep, and awaken less refreshed than with my “Vitamin D sleep”.
You write: “not being tired when I should” — when is that?
What I meant is that when I’d get into bed at night, rather than feel tired (in the sense of “an onset to sleep”, not “worn out”) I would feel either wide awake or worn out, or both. By contrast, when taking the D3, almost as soon as I would lie down in bed I would feel an onset to sleep. Yesterday morning, I took one of my leftover 50K D3 pills and last night’s sleep did seem to confirm the efficacy of the D3.
When you took the D3 once per week, you slept better every night? Or just the night after you took the D3?
To the best of my recollection, I slept well every night. I don’t recall there being any noticeable variance relative to the day I took it.
Addendum by Seth. It is impressive that two things appear true: (a) the time of day D3 is taken mattered (other stories) and (b) a dose once/week at the right time improved sleep for seven nights (this story). The combination of the two supports the idea that our sleep is controlled by an oscillator and D3 at the right time gives that oscillator a push, increasing its amplitude.