Vitamin B12

Cyanocobalamin · Methylcobalamin

Other GLP-1 peptide IM SubQ FDA/EMA Label

Half-life

6 days

Time to Peak

1 hr

Steady State

~30 days

Bioavailability

100%

Dose Range

500–5000 mcg

Frequency

Weekly

Overview

Essential B vitamin injection. Very common in the GLP-1 community — some GLP-1 medications can reduce B12 absorption over time. Also popular as a standalone energy injection in the wellness/peptide community.

Mechanism of Action

Cobalamin — essential cofactor for methionine synthase (DNA synthesis, methylation) and methylmalonyl-CoA mutase (fatty acid metabolism). Injection bypasses GI absorption issues.

Dosing Information

Route	Dose Range	Half-life	Tmax	Frequency
Intramuscular (IM)	500–5000 mcg	6 days	1 hr	Weekly, Monthly
Subcutaneous (SubQ)	500–5000 mcg	6 days	1.5 hr	Weekly, Monthly

Used in Regimens

1 regimen

Semaglutide + Metformin + B12 Support

Semaglutide GLP-1 therapy with metformin added for complementary insulin sensitisation and Vitamin B12 supplementation to offset metformin-induced B12 depletion. Growing evidence supports GLP-1 + metformin combination for enhanced weight loss and glycaemic outcomes.

B12 1000mcg/day — mandatory with metformin use.

glp1

Support

Data Sources

FDA Label Cyanocobalamin injection FDA Prescribing Information

Related Tools

Medication Level Plotter

See blood level curves for this compound

Dose Calculator

Calculate reconstitution and draw volumes

Split Dose Calculator

Divide your weekly dose into multiple injections

Track Vitamin B12 with Doseline

Reminders, medication level charts, injection site rotation, and protocol tracking — all free, all private.

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