Always consult with a qualified healthcare provider before starting any new supplement, especially if you are pregnant, nursing, taking medications, or have an underlying medical condition.
The NIH reports that only about 10 micrograms of a 500-microgram oral supplement is actually absorbed in healthy people due to limitations of stomach acid and intrinsic factor
Having the shot directly in to the muscle allows the liquid vitamin to enter the blood stream quickly, bypassing the digestive system and the gastric acids and many other obstacles anything which is taken via the mouth has to go through to reach the small intestine, for re absorption
"Human sports drug testing by mass spectrometry"
The role of magnesium and zinc in depression: similarities and differences
These observations suggest that colorectal cancer is highly sensitive to diet, and dietary interventions have potential as adjuvant therapies for colorectal cancer