It was indeed per week, for 8 weeks. If it is 5000 IU, how many days do they usually prescribe it for?
5000 IU is largely the minimum effective dose for supplementation. The FDA still recommends less than half of this, and it is a shame.
Disclaimer: I take 5k IU a day due to the past 2 decades of research on the efficacy.
Based research I've seen, for optimal wakefulness and cognitive ability, 50-60 is optimal, below 40 is too low, above 70 is too high.
You may have to adjust dosage over time to dial this in.