Back in mid-August last year, I started consistently waking up much earlier than usual. Under normal circumstances, I would wake up around 8 AM. Then, almost out of nowhere, I started waking up around 5 AM, sometimes even earlier, and couldn’t fall back asleep.
As time went by, supplements came and went from my stack, but I couldn’t fix the problem. I was desperate. I got several blood tests, including magnesium, vitamin D, and calcium. My vitamin D level was 84 ng/mL (210 nmol/L). I was also experiencing frequent urination, which eventually became another clue that helped me connect the dots.
I stopped taking all my supplements for a few weeks, but the problem persisted. Eventually, I realized that throughout this entire period, I had been taking vitamin D, magnesium, vitamin C, and B-complex almost consistently. I keep a supplement diary, which helped me identify this pattern.
After another attempt, I went almost two months without taking any of them, and my sleep finally returned to normal. I reintroduced B-complex, vitamin C, and magnesium, and the problem didn’t come back. Then I reintroduced vitamin D, and the sleep problem returned.
I had been taking around 6,000 IU of vitamin D daily for most of that time, although there were periods when I took 2,000 or 4,000 IU instead. I always took it in the morning, so taking it at night wasn’t a factor in my case.
One reason this went unnoticed for so long is that 25-hydroxyvitamin D, the main marker measured in blood tests, has a circulating half-life of approximately 2–3 weeks. This means that if your levels have become elevated, they can take months to return to normal after you stop supplementing.
I only figured this out because I’ve seen several other posts here describing similar experiences. I wanted to add my own account to the discussion, because I don’t think anyone can imagine how hellish this past year has been for me because of this.