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Vitamin B12 (test-gated)

Methyl- or cyanocobalamin

ModerateReal, but too small for your device to notice

Moderate

Some good studies, not many repeats

Why this rating

Moderate, conditional on testing: deficiency correction is well established; supplementation in replete adults is null.

2
studies
—
experiments
—
people (largest study)
2
kinds of study
In short

No effect on tiredness or thinking in people whose levels are already fine. Worth checking if you are vegan, over 50, or take metformin or stomach-acid medicine.

The bottom line

B12 is transformative if you're deficient and inert if you're not: a meta-analysis found no fatigue or cognitive benefit in people with normal levels. Vegans, adults over 50 and anyone on metformin or acid blockers should test.

How it works

Cofactor for myelin synthesis and red-cell production; deficiency causes fatigue via anemia and neuropathy.

Who it helps, and who it doesn't

Vegans/vegetarians, 50+, metformin and PPI users, post-bariatric. Test serum B12 (± MMA).

What to buy

What to look for
  • ✓Methylcobalamin or cyanocobalamin 500–1,000 µg
What to avoid
  • ✕Supplementing without a serum B12 test
Safety notes
  • ⚑ Serum B12 (± MMA)
  • · Extremely safe.

As an Amazon Associate, Umbral earns from qualifying purchases. Product data is provided by Amazon and may change; ratings and prices shown are Amazon’s, not Umbral’s. Recommendations are based on the evidence grade and the form used in trials, never on commission.

Pure Encapsulations Methylcobalamin 1,000 mcg, 60 capsules
Pure Encapsulations Methylcobalamin 1,000 mcg, 60 capsules
4.8(3,408)
$20.50

Once low is confirmed; sublingual or capsule both work.

Buy on Amazon
Amazon price on Sep 18, 2026.
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Studies over time

2 studies over 3 years

2021 — 2024
2021202220232024
Review combining many studiesControlled experimentEarly or observational studyHover a dot for details
Dose
500–1,000 µg/day if low
Timing
Any time
Where to buy

The studies

  1. 1.
  2. 2.
    Vitamin B12 — Fact Sheet for Health Professionals
    NIH Office of Dietary Supplements · 2024 · systematic review

    Risk groups, testing and dosing guidance.

Umbral is a wellness product, not a medical device. It does not diagnose, treat, cure or prevent any disease. Supplement information is educational; talk to a clinician before starting anything, especially if you are pregnant, under 18, managing a condition or taking medication.

These statements have not been evaluated by the Food and Drug Administration.