How long do I keep giving the vitamin d drops?

See below. Since we cannot store vitamin d. Once it is established that we must take it then it is forever until we start taking pills.
The first 2 years. Every breast-fed infants is recommended to take 400 iu of vitamin d supplement. The vitamin d intake in young toddlers in their 2nd year of life can be suboptimal especially if they are not offered enough dairy products. For those, supplemental vitamin d in the form of drops, would be advisable.