Vitamin manufacturing generally involves several steps including raw material sourcing, quality control, weighing and dispensing, mixing and blending, forming (e.g., tableting, encapsulation, powdering), finished product quality control, packaging, labeling, storage, and distribution. The specific process varies depending on the type of vitamin.

The human body can manufacture some vitamins, such as Vitamin D (with sunlight exposure), Vitamin K, and some B vitamins (in small amounts by gut bacteria). However, most vitamins are essential and must be obtained through diet or supplementation.

Vitamins typically have an expiration date, not just a manufacture date. This date indicates the period during which the vitamin is guaranteed to retain its full potency. It's generally recommended to use vitamins before their expiration date. The shelf life can vary depending on the specific vitamin and storage conditions   

China is a significant global producer of various vitamins and vitamin ingredients. This includes Vitamin C, many B vitamins (like B1, B2, B6, B12), Vitamin E, and Vitamin A, among others. Many supplement brands source their raw vitamin ingredients from China.

Vitamins are organic compounds that the body needs in small amounts and do not directly supply calories (energy). Calories come from macronutrients: carbohydrates, fats, and proteins.

To buy vitamins wholesale, you typically need to establish a business account with a vitamin manufacturer, distributor, or wholesale supplier. This often involves providing business documentation such as a tax ID or resale certificate. You would then be able to purchase vitamins in bulk at wholesale prices. Online wholesale marketplaces and direct contact with manufacturers are common ways to buy vitamins wholesale.