Vitamin D can be stored by the body. My Doctor also prescribed me one whole bottle every week for a certain period of time, then I switched to 6 drops a day.

Vitamin D defficiency is really a problem, I didn't know I had it till I got a blood test. I was feeling tired all the time, my bones ached, I felt low, dizzy, etc. Getting Vitamin D supplements helped cured all the symptoms, I feel much healthier now.

Yup, I was on that temporarily too. It came in little blue-and-white capsules. I think you have to get a prescription for those since, as the article mentions, large doses can cause problems over time.

I’ve been taking 60,000IU once a week for the last 3 years

Infrequent 50k IU doses are commonly used too.

yeah you can take vitamin d like that. 1 unit a day, or 7 units once a week, doesn't matter.