Vitamin D3 side effects took 2 months (!) to dissipate after being in severe deficiency

I had severe vitamin D deficiency (10 ng/ml) diagnosed in December 2023. I promptly started supplementation with 5000 IU/day the same day I got the results, and later lowered to 1000-2000 IU/day for maintenance.

The first 2 months were absolutely horrible. I was miserable - the main side effect was excessive daytime sleepiness. I was just so incredibly sleepy throughout the day, even with 8 hours of sleep. Even after napping, I was extremely tired. I was also very unmotivated and didn't even have energy for gaming, not just for work.

It went on for so long that I didn't think it could be the Vitamin D3 for so long. But it was. Somewhere in February, I just felt back to baseline, much less tired throughout the day, and I'm still doing okay even with daily supplementation now.

Magnesium had no effect whatsoever on the side effects, even though I've tried multiple forms (Citrate, Bisglycinate, Malate), nor did Vitamin K. It just took time.

If anyone else has trouble with vitamin D3 side effects after being diagnosed with a deficiency, despite taking moderate doses, hang in there! Vitamin D3 apparently behaves as a neuromodulator in the brain, affecting neurotransmitters and brain health, so it makes sense to me it takes time to get used to being sufficient after a long period of deficiency.