Especially if a person's body has trouble absorbing it, a doctor may recommend vitamin B12 injections to address a vitamin B12 deficiency
Very low body fat People with very low body fat percentages (typically below 10-12% for men or 18-20% for women) may not have sufficient subcutaneous tissue on the thigh for reliable subcutaneous injection
For context, the VITAL cohort found elevated lung cancer risk in men averaging ~127 g/day from individual B12 supplements
Any use outside of formally approved clinical trials falls outside the regulatory framework that governs medicines safety in the UK, meaning that individuals who obtain and use retatrutide independently do so without the quality assurance, standardised dosing oversight, and pharmacovigilance protections afforded by licensed medicines
There is no established tolerable upper intake level (UL), so even high-dose injections are safe because your system simply eliminates what it cannot use
For most people, daily oral methylcobalamin is more practical than chasing B12 energy shots, which are really designed for confirmed deficiency or malabsorption
