After receiving a B12 shot, there are a few things you should avoid doing. Firstly, it is important not to engage in any strenuous physical activity or exercise immediately after the shot. This is because the injection site may be sore and exercising could potentially worsen the discomfort. Additionally, it is advised not to consume alcohol for at least 24 hours after receiving a B12 shot. Alcohol can interfere with the absorption of vitamin B12 and reduce its effectiveness. Lastly, it is recommended to avoid taking any other vitamin supplements or medications without consulting with a healthcare professional first, as they may interact with the B12 shot.