A vitamin B complex injection delivers multiple B vitamins (e.g., B1, B2, B3, B5, B6, B12) directly into the bloodstream or muscle to support energy metabolism, nervous system health, and red blood cell formation. It may be prescribed for deficiencies, fatigue, or certain medical conditions. Effects vary; not a substitute for a balanced diet or medical treatment when deficiencies are severe.
Disclaimer 
This information is not medical advice. Consult a healthcare professional before use, especially if you have allergies, liver or kidney disease, pregnancy, or are taking other medications. Injections should be administered by a qualified clinician. Possible side effects include redness, swelling, or allergic reactions. Stop use and seek care if severe symptoms occur. Do not exceed prescribed dosage.