Vitamin D3 - what strength?

Hi all, I understand vitamin D is generally thought to be a good thing for MS sufferers. I have fairly benign (so far!) RRMS, and would like to keep it that way. Any idea what strength Vit D is best? I see the Highest Potency available is 5000iu, but don't want to overdo it. Are there are side effects to OD'ing on Vit D3?! Any thoughts greatly appreciated.
@The-Pond

Hi You can go a lot higher than 5000iu-I've had some that were about 14000iu! I know that too much vitamin D can be toxic though, so you don't want to overdo it. It might be worth asking to have a blood test to see what your levels are. The ones I take now are only about 1,500iu, and a recent blood test showed my levels are OK. Whatever strength you get, get them online as they'll be much cheaper (I use Big Vits or Healthspan for all my supplements). Dan

@Graham100

Hi people. I ad a blood test for Vit D & B tests came back normal, so haven't bothered taking any? Are you saying you need to take anyway??