The difference between the two is that intramuscular injections are inserted into the muscle, and subcutaneous injections are inserted just below the skin
Common side effects are typically mild and temporary: Injection site reactions (redness, slight bruising) Mild headaches (usually first week only) Temporary fatigue as your body adjusts Serious side effects are rare when protocols are followed correctly
If you experience any combination of these symptoms, particularly if you have risk factors, it is important to seek medical assessment promptly
PubMed Sikiric, P., Separovic, J., Anic, T., Buljat, G., Mikus, D., Seiwerth, S., Grabarevic, Z., Stancic-Rokotov, D., Pigac, B., Hanzevacki, M., Marovic, A., Rucman, R., Petek, M., Ziger, T., Sebecic, B., Zoricic, I., Turkovic, B., Aralica, G., Perovic, D., Duplancic, B., Lovric-Bencic, M., & Rotkvic, I