Vitamin B12
Methylcobalamin at 525 mcg. Both forms raise B12; neither has been shown clearly better for topping up a dietary gap in a healthy adult.
Written by R. Kessler · About Knurle · Editorial policy
The short answer
Vitamin B12 absorption depends on stomach acid and intrinsic factor, and saturates at a small amount per dose, which is why supplements carry large numbers: a fraction of a big oral dose gets through by passive diffusion. Both methylcobalamin and cyanocobalamin raise blood B12.
The form, and why it matters
Cyanocobalamin is cheaper, extremely stable, and is what most long-running research used. Methylcobalamin is one of the forms the body uses directly. For a healthy adult topping up a dietary gap, the evidence that one beats the other is thinner than the internet suggests.
Typical dose
The adult reference intake is 2.4 mcg a day, rising in pregnancy and breastfeeding. Absorption through intrinsic factor saturates around 1.5 to 2 mcg per dose, so supplements supply far more and rely on passive diffusion for the remainder. Keel carries 525 mcg.
What the research shows
Long-term metformin use has a well-documented association with lower B12, including in the Diabetes Prevention Program Outcomes Study. GLP-1 receptor agonists have not been shown to deplete B12 directly; the issue on those medications is intake, because eating less food means less B12 arriving with it.
Who should be careful
B12 testing is the honest starting point: a serum B12, sometimes with methylmalonic acid if the result is borderline. Supplementing heavily before testing can make the result harder to read. People with pernicious anaemia or after certain bowel surgeries may need injections, which is a prescriber's call.
Where it sits in our formulas
| Product | Form on the label | Amount per serving | % Daily Value |
|---|---|---|---|
| Keel | as methylcobalamin | 525 mcg | 21875% |
Sources
- NIH Office of Dietary Supplements, Vitamin B12 fact sheet
- Aroda et al., long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study, Journal of Clinical Endocrinology and Metabolism
Figures checked against the sources above on 21 September 2026.
Folate
L-5-MTHF-Ca at 400 mcg DFE, the active form. High folate can mask a B12 shortfall on a blood count, which is why the two travel together.
Read itVitamin B6
Pyridoxal 5′-phosphate, the active form. Keel carries a high 26 mg because it sits inside a blend designed for people eating far less.
Read itIron
Ferrous bisglycinate at 18 mg, a chelated form that is usually kinder to the stomach than oxide or sulfate at the same elemental amount.
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Read itMethylated B12, folate and B6: when form matters
Why methylcobalamin, L-5-MTHF-Ca and P5P instead of cyanocobalamin, folic acid and plain B6. Active forms, homocysteine, and the MTHFR story plainly told.
Read itMethylcobalamin vs cyanocobalamin: which is better
Cyanocobalamin is stable, cheap, and used in most of the research. Methylcobalamin is already active. For topping up a dietary gap, the evidence that one beats the other is thinner than the internet suggests.
Read itEvery milligram, printed.
Each amount on the label is the amount in a full daily serving, and it matches what is on this page.
