Convenience

• Vitamin C powder must be mixed into a glass of water, and usually must be stirred for 30 to 60 seconds before dissolving completely.
  
  

Fillers

• Vitamin C pills commonly contain fillers and binding agents such as corn starch, hydroxypropyl methylcellulose, and polyethylene glycol, which could potentially (albeit rarely) trigger allergies or side effects. Hydroxypropyl methylcellulose has also been petitioned against for the usage of hazardous materials in its production.
  
  

Absorption

• A small study, according to Oregon State University, found no difference in the body's rate of absorption between vitamin C powder, tablets and chewable tablets.
  
  

Oral Mega-Dosing

• The practice of "mega-dosing", as pioneered by Linus Pauling, is usually done with a powder because it involves drinking a solution rather than swallowing a large number of pills. Any effects from the fillers and binders in pills are also compounded at large doses.
  
  

Intravenous Mega-Dosing

• Intravenous vitamin C, prepared only from powder form, is used by select doctors to treat various diseases including cancer. Hugh Riordan, M.D. claims to have treated over 2,000 patients with 60 to 120 grams of intravenous sodium ascorbate without problems.