The best way to correct a deficiency of Vitamin B12 is through a Vitamin/Nutrient IV that contains vitamin B12 and/or via vitamin B12 injections
However, some studies have safely used 2 to 12 milligrams daily

Major Ingredients Water, Triethylhexanoin, Hydrogenated Poly(C6-14 Olefin), Butylene Glycol, Niacinamide, Methylpropanediol, 1,2-Hexanediol, Phenyl Trimethicone, Diethoxyethyl Succinate, Polyglyceryl-10 Myristate, Borago Officinalis Extract, Centaurea Cyanus Flower Extract, Chamomilla Recutita (Matricaria) Flower/Leaf Extract, Lavandula Angustifolia (Lavender) Flower Water, Hyacinthus Orientalis (Hyacinth) Extract, Salvia Sclarea (Clary) Extract, Ethylhexylglycerin, Hibiscus Esculentus Fruit Extract, Corchorus Olitorius Leaf Extract, Carum Petroselinum (Parsley) Extract, Hexyl Cinnamal, Limonene, Linalool, Fragrance, Hippophae Rhamnoides Oil, Allantoin, Hydrogenated Lecithin, Sodium Gluconate, Glutathione, Adenosine, Cellulose Gum, Melia Azadirachta Leaf Extract, Melia Azadirachta Flower Extract, Curcuma Longa (Turmeric) Root Extract, Ocimum Sanctum Leaf Extract, Corallina Officinalis Extract, Biotin, Biotinoyl Tripeptide-1, Acetyl Hexapeptide-8, Tripeptide-1, Tripeptide-3, Myristoyl Pentapeptide-17, Hexapeptide-9, Gluconolactone, Alpha-Arbutin, Thioctic Acid Ingredients subject to change at manufacturer's discretion

In the shots I tried, I only had one issue where it left a bruise because I got all tense and freaked myself out so I went in the muscle
However, based on the research to date, researchers will want to consider the following guidelines when when administering these peptides: Subcutaneous and intramuscular injections are considered more effective due to enhanced bioavailability , but using BPC-157 + TB-500 nasal spray could have certain advantages depending on the therapeutic objective and study design
They are especially suitable for individuals needing ongoing, maintenance-level doses of B12