They may recommend adjusting the dosage, using a different form of B12, or exploring other supplementation methods, such as oral supplements or patches
doi:10.1016/s0083-6729(00)59012-8
Headache Mild diarrhea Mild pain or redness at the injection site Nausea Serious or rare side effects Stop taking Vitamin B12 Injection and seek immediate medical attention right away if you experience any of the following: Allergic reactions, including angioedema, hives, and trouble breathing Signs of heart problems, including swelling, rapid weight gain, and shortness of breath Signs of hypokalemia, including muscle weakness, slow or irregular heartbeat Contraindications: This is not an exhaustive list of contraindications
note in Nature Medicine , NNMT inhibition has been shown to enhance energy expenditure and promote fat loss, even without dietary modification (Kraus et al., Nature Medicine )