Vitamin D likely plays a role in the geography of Multiple Sclerosis (MS), and patients at risk and with MS have relatively low Vitamin D levels compared to their normal counterparts.

This trial examines the safety of high dose oral Vitamin D3 titrated up to a maximum of 40,000 IU per day over a 12 month period. Fifty patients matched for MS and non-MS characteristics will be divided into two groups: one group receiving the high dose Vitamin D regimen, and the other restricted to a maximum of 4000 IU per day. The hypothesis is that patients with MS can tolerate seemingly high doses of Vitamin D3 without adverse events and/or calcium-related abnormalities. It is also hypothesized that those receiving the higher doses will demonstrate improved relapse and disability status compared to controls, and that the treatment group will show improved markers of bone health and immune indicators of reduced inflammation.

Inclusion Criteria:

• Clinically definite MS
• Age 18-55
• EDSS 0-6.5

Exclusion Criteria:

• EDSS => 7.0
• Current Vitamin D3 use >4000 IU/d
• Baseline (25(OH)D) level <20 mmol/L (frank deficiency) and >150 mmol/L
• Pregnancy or inability/unwillingness to use contraception
• History of cardiac arrhythmia
• History of renal disease and nephrolithiasis
• History of granulomatous disease or lymphoma
• Relapse activity or steroid use in the past 60 days