All delivered intravenously so they reach your immune system immediately
While deficiencies take time to develop, people with gastrointestinal disorders, low stomach acid (common with aging), or those following vegan or vegetarian diets may struggle to get enough B12
Progress May Be Gradual Wellness programs should not be expected to produce immediate or dramatic changes
(12) M Macvanin, Z Gluvic, J Radovanovic, M Essack, et al (2023) New insights on the cardiovascular effects of IGF-1 Frontiers in Endocrinology (Lausanne), 2023 Feb 9, Volume 14, Page 1142644
The abdomen also tends to have less nerve density than the thigh at the specific insertion points used, which translates to less sensation during injection
Note that the peak concentration occurs when the absorption rate is equal to the elimination rate at around 1.5 hours