Injections provide a direct and concentrated dose of vitamin D3, leading to a quicker increase in blood levels compared to oral supplements. This increased absorption of D3 can lead to improved bone health, immune function, muscle health, and mood. Furthermore, individuals with chronic conditions such as multiple sclerosis, rheumatoid arthritis, or chronic kidney disease, maintaining adequate vitamin D levels is important. Intramuscular (IM) injections for increased absorption.