There is a chart at this link
That enables you to work out how many EXTRA iu of Vitamin D3 per KG of your current weight may be required to reach a 25(OH)D above 125nmol/l
It’s at 125nmol/l (50ng/ml) that Vitamin D is most effective as an anti-inflammatory agent and MS progression and disability is driven by inflammation. and the inflammatory response.
Allow 3~5 months at the higher daily vitamin D3 intake and then retest and adjust the daily dose again.
I agree with rizzo that if you are aiming for 150nmol/l it may be sensible to go straight for 10,000iu/daily and retest sooner than 3 months. 150 nmol/l gives you a bigger reserve if you fall ill or have an accident and your body uses up it’s vitamin D reserves dealing with a crisis. Below 100nmol/l the body only has a few days vitamin D and there is no spare Vitamin D3 available as it’s all being accounted for meeting your body’s daily needs.