life extension glutathione cysteine & c Nutricost N-Acetyl L-Cysteine (NAC) 600mg, 180 Capsules Willner Chemists | Life Extension
Description
View Study PCO-02 Safety and Pharmacokinetics Trial (Phase 1)

Its not a collapse its a recalibration

Once in the bloodstream, B12 attaches to transporter proteins, like holotranscobalamin (TC-Cbl), which carry it to cells where it supports functions such as DNA synthesis, cell growth, and energy production

Also, 500mg per day is an effective dose but up to 2,000 mg has been shown to have additional benefits
Kaye, E
