Oral has felt very effective for me. I take a daily supplement that has roughly 100% of the recommended daily dose of everything. I split it in half.

For D3, it is 25mcg / 1000 IU / 125%

After splitting in half it's 12.5 mcg / 500 IU / 62.5%.

I take with some fat-containing food to allow ir to absorb which is usually breakfast (yogurt, some nuts, some kind of fruit, oats), and it's a night and day difference in my mood (how easily I can control my temper if already agitated, how easily I brush off annoying stuff, takes the intensity off of my reactions and mood during conversations).

I did a blood test before starting, and if normal is between 30 - 70, I was at 10. Dr prescribed megadose of D2, followed by daily D3, but I skipped on the megadose and went straight to D3 -- makes me wonder if a megadose would build up my stores since D is fat-soluble and make it so I could miss a day and not notice.

All of the above is anecdotal from me, a self-professed cave dweller, but it's been a couple of years now, and I still notice the difference. Also, what I heard from people in Boston is that 90% of them are on a vitamin D supplement. My friend from there laughed at me when I was raving about it, saying "yeah, literally everyone here is on it".