Overdose of vitamin D

He's told you to use the lot at once because to improve a very low vit D level you need high doses - 3 x 20,000 IU per week for several weeks is normal, then a blood test to see if the level has come up to normal.

The 200-400 IU/day is at the low end of the daily recommended amount - and since I don't know how much is in it per ml I can't work out what the 15 ml dose is - but it is fine to take the lot at once since you are very deficient at 17 ng/ml.

Once you have finished the 4 bottles I imagine he will give you tablets - but since the usual tablets are large for chewing, taking 2 tablets per day to get 800 IU/day you'd need to chew a lot to get a high dose! The bottle is far easier.

My vitamin D reading was 17 too and my doctor prescribed 2x20,000 IU tablets a week for 8 weeks so your doctor doesn't seem to have given you too high a dose to take. I hope my maths calculation from Mcg to IU is correct, When my next blood test was taken after I had finished the course my reading was 75. 

1ml Vidrops supplement = 2,800 IU vitamin D X 15ml = 42,000IU vitamin D total per bottle. 

Vitamin D deficiency is usually treated with 50,000 - 70,000IU/wk for 8-12 weeks, so this is an appropriate dose for deficiency. My doctor gave me a 50K IU pill to take once weekly. It's just easier not to miss doses this way - one big thing to remember every week, but it really won't make any difference if you space out your dose and take it daily, just as long as you get the recommended dose over the course of the week. 

I just hope, for your sake, that it doesn't taste too bad!