Vitamin B12 Deficiency: Methylcobalamin, Vegans, Metformin, and Tests
Vitamin B12 (methylcobalamin) guide: nerve myelin, homocysteine, vegan and metformin deficiency testing (MMA & holoTC), and NOW Methyl B-12 on Amazon.
Methylcobalamin vs cyanocobalamin, who actually needs a lozenge, and why vegans cannot skip this one
Vitamin B12 is required for myelin, DNA synthesis, and homocysteine handling. Deficiency is a neuropathy and anemia problem — not a focus hack. This guide covers who needs a lozenge, what to test, and why NOW methyl 1,000 mcg is enough for most plant-based eaters.
Health Disclaimer
This content is for general informational and educational purposes only. It is not medical advice, diagnosis, or treatment. Consult a qualified healthcare provider before starting any supplement, peptide, or health protocol. Read our full health disclaimer.
Frequency
Daily lozenge if diet or labs say so
Duration
Ongoing on vegan diets; reassess after labs if omnivore
Level
Beginner
Key Takeaways
- 1Vegan diets, metformin, PPIs, and older adults are the usual reasons to supplement
- 2Test B12 and MMA if symptoms or diet risk — do not megadose for ‘energy’ if replete
- 3Methylcobalamin and cyanocobalamin both work; pick a cheap lozenge you will use
- 4Greger will let you skip most capsules; he will not let you skip B12
Who this is for
- ·Plant-based eaters building a Daily Dozen kitchen
- ·Anyone with a low B12 or high MMA
- ·Omnivores who were sold B12 as a pre-workout
Who Needs It
Strong EvidenceAnimal foods are the reliable dietary source. A strict plant-based diet without a supplement is a planned deficiency.
Metformin, proton-pump inhibitors, and atrophic gastritis impair absorption. Age-related intrinsic-factor decline is why many clinicians supplement older adults even if they eat meat.
Forms and Dose
Strong EvidenceCyanocobalamin is cheap and well-studied. Methylcobalamin is the coenzyme form in NOW’s lozenge. For almost everyone the difference is branding.
1,000 mcg daily is a convenient lozenge, far above the RDA, and appropriate as vegan insurance. Correcting frank deficiency may use injections — that is a clinician call.
Labs
Moderate EvidenceSerum B12 can look ‘normal’ while MMA is high. If neuropathy or anemia is in play, ask for MMA and a proper workup — high-dose lozenges can mask folate issues on some panels.
As an Amazon Associate, Reo Tuku Iho Limited earns from qualifying purchases through Amazon links on this site. Full disclosure
For educational purposes only. Not medical advice. Read our health disclaimer.
Sources
Key references cited in this guide. Links open the original publication or abstract.
- Vitamin B12 deficiency — reviewAm Fam Physician, 2013
Continue Reading
SupplementsMethylfolate (5-MTHF) Guide: Daily Dose, MTHFR & Who Should Avoid It
Methylfolate (5-MTHF) is the biologically active form of folate (vitamin B9). How much L-methylfolate should you take daily, when should you take it, and who should not take methylfolate? Typical maintenance dosing is 400–1,000 mcg taken in the morning with breakfast alongside active Vitamin B12 ([NOW Methyl B-12](/equipment/now-foods-methyl-b12)). Never take high-dose folate with an uncorrected B12 deficiency, seizure medications without physician oversight, or methotrexate.
Read guide
SupplementsWhat Is How Not to Die? Greger's Daily Dozen Checklist
How Not to Die (2015) is NutritionFacts.org in hardcover: fifteen causes of death and the plant foods Greger wants on your plate. The Daily Dozen is the useful protocol. This guide separates strong diet-pattern evidence from ‘reverse disease with broccoli’ headlines and links the book plus olive oil, fiber, and matcha.
Read guide
SupplementsWhat Is How Not to Age? AMPK, Autophagy, Fiber, and Spermidine
How Not to Age (2023) is NutritionFacts.org aimed at hallmarks of aging: autophagy, senescent cells, AMPK, and centenarian patterns. The useful protocol is still plants, fiber, and skipping boutique serums. This guide extracts the grocery list and flags where ‘disrupt every pathway’ overreaches.
Read guide
SupplementsVitamin D Dose: Test 25(OH)D, Target 40–60 ng/mL, and Pair with K2
Vitamin D is technically a hormone, involved in immunity, bone health, mood, and 200+ gene expressions. Deficiency affects ~40% of adults in temperate climates. This guide covers testing, dosing, K2 pairing, and sun vs supplement tradeoffs.
Read guideSupplementsBest Vitamin D3: 5,000 IU, K2, and a 40–60 ng/mL Lab Target
Vitamin D shopping is easy once you have a 25(OH)D number. D3 (cholecalciferol) beats D2. 5,000 IU is a repletion-style softgel, not a forever default. This buying guide picks NOW D3 for cheap D-only and Thorne D3/K2 when you want both in one capsule.
Read guide
SupplementsHow Much Protein for Longevity? 1.6–2.2 g/kg and Leucine
Protein is the most under-discussed longevity lever after sleep and training. Too little accelerates sarcopenia; the right amount supports muscle, bone, and metabolic health into older decades. This guide covers g/kg targets, meal distribution, and how protein needs change on GLP-1s and during fat loss.
Read guideLast updated: 2026-09-22 · For informational purposes only. Not medical advice. Consult a healthcare provider before starting any new health protocol. Health disclaimer.