Or at least 4 days, you can start to see your levels at 4 days. I would not add a whole lump at one time, start with 1/3 or 1/2 of the recommended dose and check after 4 days. If its reaching close to your level, pull it out of there as it can often rise more in the next couple days even without the extra still in there. Easy to add more if you need it, hard to remove (drain and refill)