What is the recommended dose of Vitamin B12?

- **RDA (adults >13):** 2.4 μg/day - **RDA (pregnant):** 2.6 μg/day - **RDA (lactating):** 2.8 μg/day - **OTC supplements:** 500-2,000 μg per tablet (far above RDA — excess is excreted in urine) - ...

Is Vitamin B12 safe to take daily?

Vitamin B12 is rated "Prescription Interactions" based on clinical evidence. - **At typical oral doses:** Very safe. Side effects uncommon. - **At high oral doses (1,000 μg+):** Mild GI symptoms (nausea, diarrhea, abdominal pain), headache - **Acneiform eruptions:** Vitamin B12 can cause acne-like l

Does Vitamin B12 interact with any medications?

Vitamin B12 has 2 known drug interactions, including interactions with Drugs that cause hypokalemia (diuretics, laxatives), Supplements that cause hypokalemia. Check with your doctor before combining with prescription medications.

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Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Vitamin B12

LIMITED EVIDENCEVitaminLast updated April 5, 2026

SCAN DOSE SUMMARY

Vitamin B12 is an essential water-soluble vitamin critical for nerve function, DNA synthesis, and red blood cell production. Here's the honest truth: if you're not deficient, supplementing B12 does almost nothing. The evidence database is full of Grade D (no effect) ratings for cognition, depression, and fatigue in non-deficient people. But deficiency is common — especially in vegans, older adults, and people on metformin or acid-reducing drugs — and can cause irreversible nerve damage if untreated. Know your levels before supplementing.

EVIDENCE GRADES

Depression SymptomsNo effect — 5 studies, 2,912 participants

CognitionNo effect — 9 studies, 2,912 participants

FatigueNo effect

Stroke RecoveryLimited — 1 study, 14 participants

Homocysteine reductionNo effect at typical doses

WHAT IT DOES

Prevents/treats B12 deficiency — The only proven indication. Deficiency causes megaloblastic anemia, neurological damage, fatigue, and cognitive decline.
Does NOT improve cognition in non-deficient people — Grade D across 9 studies.
Does NOT improve depression in non-deficient people — Grade D across 5 studies.
Does NOT reduce fatigue in non-deficient people — Grade D.
Essential for: Nerve myelination, DNA synthesis, red blood cell production, homocysteine metabolism.

OPTIMAL DOSAGE

RDA (adults >13): 2.4 μg/day
RDA (pregnant): 2.6 μg/day
RDA (lactating): 2.8 μg/day
OTC supplements: 500-2,000 μg per tablet (far above RDA — excess is excreted in urine)
For deficiency treatment (injection): 1,000 μg IM 3x/week for 2 weeks → weekly for 4 weeks → monthly maintenance
No established UL: Water-soluble; excess excreted. Generally safe even at high doses.
Best forms: Methylcobalamin (active form, preferred for neurological support), cyanocobalamin (most stable, most studied, cheapest), hydroxocobalamin (longer-acting injection form)
Timing: Any time of day. Can be taken with or without food.
Storage note: B12 supplements degrade with light, heat, and oxidation. Store in cool, dark, airtight container. Cyanocobalamin is most stable.

Scan a supplement containing Vitamin B12

DRUG INTERACTIONS

Drugs that cause hypokalemia (diuretics, laxatives)Severe

Additive potassium lowering

Monitor potassium when starting IM B12 for anemia. Oral supplementation not a concern.

Supplements that cause hypokalemiaSevere

Additive potassium lowering

Monitor potassium.

SAFETY PROFILE

Side Effects

At typical oral doses: Very safe. Side effects uncommon.
At high oral doses (1,000 μg+): Mild GI symptoms (nausea, diarrhea, abdominal pain), headache
Acneiform eruptions: Vitamin B12 can cause acne-like lesions (comedones, papules, pustules) in atypical locations. Not responsive to standard acne treatments. Resolves when B12 is stopped.
Allergic reactions (rare): Itching, hives, tongue swelling, shortness of breath, hypotension. Uncommon but can range to life-threatening.
Hypokalemia (IM route only): When treating severe megaloblastic anemia, B12 injections can temporarily lower potassium as new red blood cells are rapidly produced.

Drug Interactions

Key insight: B12 has remarkably few drug interactions. However, many drugs deplete B12 — see below.

Nutrient Depletions (Drugs That Deplete B12)

Metformin — can reduce B12 levels. Mechanism involves calcium-dependent absorption. Supplementation effective. Calcium supplementation may also help.
Acid-lowering drugs (PPIs: omeprazole, lansoprazole; H2RAs: famotidine, ranitidine) — reduce B12 absorption from food by lowering stomach acid. Supplemental B12 (not food-bound) is not affected. Clinical significance debated.

Precautions

Pregnancy: Safe. Supplementation often recommended, especially for vegans/vegetarians. Deficiency can cause poor outcomes for the baby.
Breastfeeding: Safe. B12 is naturally in breast milk.
Myeloproliferative disorders (polycythemia vera): Avoid. B12 increases red blood cell production, which can worsen these rare blood cancers.
Leber disease (genetic optic neuropathy): Avoid. May worsen optic atrophy.
Impaired kidney function: Caution. Some cyanocobalamin supplements contain aluminum, which can accumulate and cause CNS toxicity in people with kidney impairment.
Diabetic nephropathy: High doses (1,000 μg) might worsen kidney function. More research needed.

WADA Status

Not Prohibited. Not on the 2026 WADA list.

WHO SHOULD BE CAREFUL

HOW SCAN DOSE SCORES THIS

Present in proper dose (2.4-1,000 μg):✅ Green flag — safe, essential vitamin. Important for at-risk groups (vegans, elderly, metformin users).

Underdosed (<1 μg):⚠️ Yellow flag — below RDA

Cyanocobalamin in kidney disease patient:⚠️ Yellow flag — aluminum accumulation risk

In a proprietary blend:Neutral — B12 is safe at a wide dose range, so blend risk is lower than most supplements

Marketed for energy/cognition in general population:⚠️ Yellow flag — evidence does NOT support benefits in non-deficient people. Misleading marketing.

CLINICAL REFERENCES

Comprehensive review. B12 deficiency affects 6% of adults <60 and nearly 20% of those >60. Can cause irreversible neurological damage if untreated.

Green R et al. Vitamin B12 deficiency.. Nat Rev Dis Primers (2017). PMID: 34207137

Vegans and vegetarians are at high risk of B12 deficiency. Supplementation is essential for these populations.

Rizzo G et al. Vitamin B12 among Vegetarians: Status, Assessment and Supplementation.. Nutrients (2016). PMID: 33847393

Serum B12 levels <200 pg/mL indicate deficiency. Methylmalonic acid is the most sensitive confirmatory test.

Langan RC et al. Update on Vitamin B12 Deficiency.. Am Fam Physician (2017). PMID: 29248320

Long-term metformin use significantly associated with B12 deficiency. Periodic monitoring recommended.

Aroda VR et al. Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study.. J Clin Endocrinol Metab (2016). PMID: 28660890

B12 supplementation alone does not improve cognition or mood in non-deficient populations.

Ford TC et al. The Effect of Vitamin B Supplementation on Mood, Cognition, and Well-being in Healthy Adults.. Nutr Neurosci (2018). PMID: 34521255

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Quality Testing Intelligence

Based on independent third-party laboratory analysis

Category pass rate: ~75%. Dose accuracy and dissolution are the main issues.

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Independently graded against 173,636 indexed supplements with 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: April 5, 2026

Not medical advice. Based on published clinical research and systematic reviews.

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Ingredient Research

Graded against 173,636 supplements + 177 published clinical interactions, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

Vitamin B12

LIMITED EVIDENCEVitaminLast updated April 5, 2026

SCAN DOSE SUMMARY

EVIDENCE GRADES

Depression SymptomsNo effect — 5 studies, 2,912 participants

CognitionNo effect — 9 studies, 2,912 participants

FatigueNo effect

Stroke RecoveryLimited — 1 study, 14 participants

Homocysteine reductionNo effect at typical doses

WHAT IT DOES

Prevents/treats B12 deficiency — The only proven indication. Deficiency causes megaloblastic anemia, neurological damage, fatigue, and cognitive decline.
Does NOT improve cognition in non-deficient people — Grade D across 9 studies.
Does NOT improve depression in non-deficient people — Grade D across 5 studies.
Does NOT reduce fatigue in non-deficient people — Grade D.
Essential for: Nerve myelination, DNA synthesis, red blood cell production, homocysteine metabolism.

OPTIMAL DOSAGE

RDA (adults >13): 2.4 μg/day
RDA (pregnant): 2.6 μg/day
RDA (lactating): 2.8 μg/day
OTC supplements: 500-2,000 μg per tablet (far above RDA — excess is excreted in urine)
For deficiency treatment (injection): 1,000 μg IM 3x/week for 2 weeks → weekly for 4 weeks → monthly maintenance
No established UL: Water-soluble; excess excreted. Generally safe even at high doses.
Best forms: Methylcobalamin (active form, preferred for neurological support), cyanocobalamin (most stable, most studied, cheapest), hydroxocobalamin (longer-acting injection form)
Timing: Any time of day. Can be taken with or without food.
Storage note: B12 supplements degrade with light, heat, and oxidation. Store in cool, dark, airtight container. Cyanocobalamin is most stable.

Scan a supplement containing Vitamin B12

DRUG INTERACTIONS

Drugs that cause hypokalemia (diuretics, laxatives)Severe

Additive potassium lowering

Monitor potassium when starting IM B12 for anemia. Oral supplementation not a concern.

Supplements that cause hypokalemiaSevere

Additive potassium lowering

Monitor potassium.

SAFETY PROFILE

Side Effects

At typical oral doses: Very safe. Side effects uncommon.
At high oral doses (1,000 μg+): Mild GI symptoms (nausea, diarrhea, abdominal pain), headache
Acneiform eruptions: Vitamin B12 can cause acne-like lesions (comedones, papules, pustules) in atypical locations. Not responsive to standard acne treatments. Resolves when B12 is stopped.
Allergic reactions (rare): Itching, hives, tongue swelling, shortness of breath, hypotension. Uncommon but can range to life-threatening.
Hypokalemia (IM route only): When treating severe megaloblastic anemia, B12 injections can temporarily lower potassium as new red blood cells are rapidly produced.

Drug Interactions

Key insight: B12 has remarkably few drug interactions. However, many drugs deplete B12 — see below.

Nutrient Depletions (Drugs That Deplete B12)

Metformin — can reduce B12 levels. Mechanism involves calcium-dependent absorption. Supplementation effective. Calcium supplementation may also help.
Acid-lowering drugs (PPIs: omeprazole, lansoprazole; H2RAs: famotidine, ranitidine) — reduce B12 absorption from food by lowering stomach acid. Supplemental B12 (not food-bound) is not affected. Clinical significance debated.

Precautions

Pregnancy: Safe. Supplementation often recommended, especially for vegans/vegetarians. Deficiency can cause poor outcomes for the baby.
Breastfeeding: Safe. B12 is naturally in breast milk.
Myeloproliferative disorders (polycythemia vera): Avoid. B12 increases red blood cell production, which can worsen these rare blood cancers.
Leber disease (genetic optic neuropathy): Avoid. May worsen optic atrophy.
Impaired kidney function: Caution. Some cyanocobalamin supplements contain aluminum, which can accumulate and cause CNS toxicity in people with kidney impairment.
Diabetic nephropathy: High doses (1,000 μg) might worsen kidney function. More research needed.