B12

Why experts recommend 700–900 pg/mL for vegans

A serum vitamin B12 level in the range of 700 to 900 pmol/L is considered optimal (above the standard "normal" range) for vegans because it ensures ample supply for critical functions and helps prevent subtle signs of deficiency that may be masked by their typically high-folate diets.

Vegans do not get natural B12 from:

  • meat

  • eggs

  • dairy

  • fish

So they rely on:

  • fortified foods

  • supplements

  • nutritional yeast

But food-based B12 absorption can be inconsistent.

Studies show vegans often need:

  • higher circulating B12

  • to maintain adequate active B12 and low MMA

Functional markers (MMA and homocysteine) start to become abnormal when serum B12 drops below ~500–600 pg/mL — even if the number is still “normal” on the lab sheet.

That is why experts suggest aiming for 700–900 pg/mL.

Vegans need more serum B12 to achieve the same cellular levels

Only about 20% of serum B12 is active (holotranscobalamin).

The rest is bound to haptocorrin and not usable.

In vegans:

  • active B12 can be lower

  • total B12 fluctuates more

  • MMA rises sooner

  • nerve symptoms appear at higher serum levels than in omnivores

So a vegan with a serum level of 600 may have the same functional B12 status as an omnivore with a level of 500.

That’s why the target is bumped slightly higher.

Sometimes "normal" is not "optimal"

This is true for many nutrients:

  • Ferritin: normal ≠ optimal

  • Vitamin D: normal ≠ optimal

  • B12: normal ≠ optimal

609 pg/mL (11/20/2025 lab result) is healthy and acceptable, but 700–900 pg/mL provides extra protection, especially for:

  • vegans

  • older adults

  • people with Hashimoto’s (absorption varies year to year)

  • people avoiding fortified dairy/soy

  • people with GI issues

  • people not taking multivitamins


609 pg/mL = normal, healthy, totally fine

(based on general population statistics)

700–900 pg/mL = optimal for vegans and people with fluctuating absorption

(based on functional studies showing better MMA and nerve protection)

Your plan to take 500 mcg twice weekly is the perfect strategy:

  • It won’t push your levels too high

  • It will gently maintain you in the optimal range

  • It supports long-term neurological and metabolic health


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