Across 3,058 first-hand reports, people mentioned a side effect 106 times (about 3 per 100 reports). The most common: insomnia, anxiety, hypercalcemia. User reports show what people notice — they can't tell you whether Vitamin D is safe for you.
“I'm able to take about 400 ius of Vitamin D per day. Anything beyond that, and I become very angry/rageful and feel mentally terrible.”
“I was taking 30,000 IU day sometimes...for the past 2 years, my sleep has basically been murdered.”
“The only tangible thing I ever found...is a vitamin d deficiency but even with supplementing...there was little to no improvement.”
“started getting what i can only describe as mania. Super elevated mood, abundance of energy.”
“She put me on a once-weekly 15,000 IU supplement for a month to boost my D3 levels and I could tell a difference immediately.”
“It changed my life. Anxiety, insomnia, tinnitus, muscle cramps, joint aches, sense of dread, exhaustion are gone.”
Conclusion: Vitamin D deficiency and insufficiency are associated with miscarriage. Whether preconception treatment of vitamin D deficiency protects against pregnancy loss in women at risk of miscarriage remains unknown.
Conclusion: In adults with prediabetes, vitamin D was effective in decreasing risk for diabetes.