This can be due to a number of factors, including pernicious anemia, Crohns disease, and celiac disease
(Native, unmodified recombinant human IGF-1, sold as mecasermin/Increlex, is FDA-approved only for a narrow pediatric growth-failure indication and is chemically distinct from the LR3 analog.) In the US it is manufactured and sold almost exclusively as an unregulated "research chemical" labeled "not for human consumption," a labeling practice peptide vendors use to avoid marketing it as an unapproved drug
These products are for research use only and are not intended for human consumption, therapeutic use, or diagnostic purposes
That said, a daily multivitamin (or the prenatal vitamin you took while you were pregnant) can act as an insurance policy to help fill in any nutritional gaps
The reason is unapologetically unglamorous and worth understanding
Most compounded tirzepatide with B12 remains stable for 28-42 days when refrigerated properly