Suomeksi

Vitamin B12 (cyanocobalamin): dosage in studies

Updated 15 Oct 2026 Author: About 2 min read Drafted with the help of AI; sources and claims checked separately.

Not a recommendation, not treatment guidance. This page shows only what published human studies used, with sources. This site does not say how much anyone should use of any substance. Fimea warns against using injectable peptides bought online: Fimea warning.

Finland has an authorised cyanocobalamin product taken by mouth. This page shows only doses used in studies, not the approved doses of that product [8]regulator.

In randomised trials, vitamin B12 deficiency was treated with cyanocobalamin either every day by mouth or as injections into a muscle, and the response was followed with blood tests [1, 2, 3]A.

In one placebo-controlled trial, cyanocobalamin was injected once into a muscle in singers who had no deficiency [4]A.

Doses used in studies

Doses used in published human studies. Not a recommendation.
StudyParticipantsDoseFrequencyDurationSource and level
Kuzminski 1998 (randomised), by mouth 18 evaluable patients with B12 deficiency 2 mg cyanocobalamin by mouth Daily 120 days [1]A
Kuzminski 1998 (randomised), into a muscle 15 evaluable patients with B12 deficiency 1 mg cyanocobalamin into a muscle On days 1, 3, 7, 10, 14, 21, 30, 60 and 90 90 days [1]A
Eussen 2005 (randomised, double-blind) 120 older people with mild B12 deficiency 2.5, 100, 250, 500 or 1,000 µg cyanocobalamin by mouth (by group) Daily 16 weeks [2]A
OB12 2020 (randomised), by mouth 140 people aged 65 or over with B12 deficiency 1 mg cyanocobalamin by mouth Daily in weeks 1-8, then once a week 52 weeks [3]A
OB12 2020 (randomised), into a muscle 143 people aged 65 or over with B12 deficiency 1 mg cyanocobalamin into a muscle Every other day in weeks 1-2, once a week in weeks 3-8, then once a month 52 weeks [3]A
Shoffel-Havakuk 2021 (randomised, placebo, crossover) 20 singers without B12 deficiency 1,000 µg cyanocobalamin into a muscle (deltoid); salt solution in the other period Single dose One week of follow-up, at least 4 weeks between periods [4]A

Evidence levels: regulator = a regulator's assessment or decision, not research evidence · A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed

Units: µg = microgram, written mcg in the calculator. A milligram (mg) is a thousand times larger.

Notes

In the Kuzminski trial, 2 mg by mouth every day was as effective as the injections and raised blood B12 higher at four months (1,005 vs 325 pg/mL) [1]A.

In the Eussen trial, methylmalonic acid fell by 16, 16, 23, 33 and 33 per cent at doses of 2.5-1,000 µg. Correcting mild deficiency needed 647-1,032 µg a day, more than 200 times the recommended daily intake [2]A.

In the three trials of the Cochrane review, doses and dosing frequency varied, and the results could not be pooled. The quality of the evidence was low [5]A.

What points the other way or is uncertain

In the OB12 trial at one year, 73.6 per cent of the tablet group and 80.4 per cent of the injection group had a normal B12 level, and the tablet could not be shown to be at least as good when it was taken once a week after week eight [3]A.

Without a deficiency, a 1,000 µg injection did not differ from a placebo injection in singers' voice symptoms [4]A, and B12 supplements did not improve memory or mood in 16 randomised trials [6]A.

In diabetic kidney disease, 1 mg of vitamin B12 a day together with folic acid and vitamin B6 sped up the decline of kidney function and increased vascular events [7]A.

More on this

Read the research yourself: sources

  1. Kuzminski AM, Del Giacco EJ, Allen RH, et al. Effective treatment of cobalamin deficiency with oral cobalamin. Blood. 1998;92(4):1191-1198. PMID 9694707
  2. Eussen SJ, de Groot LC, Clarke R, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dose-finding trial. Arch Intern Med. 2005;165(10):1167-1172. PMID 15911731
  3. Sanz-Cuesta T, Escortell-Mayor E, Cura-Gonzalez I, et al. Oral versus intramuscular administration of vitamin B12 for vitamin B12 deficiency in primary care: a pragmatic, randomised, non-inferiority clinical trial (OB12). BMJ Open. 2020;10(8):e033687. PMID 32819927
  4. Shoffel-Havakuk H, Lava CX, Reuven Y, et al. Effect of Vitamin B12 Injection on the Vocal Performance of Professional Singers: A Randomized, Double-blind, Placebo-Controlled, Crossover Trial. JAMA Otolaryngol Head Neck Surg. 2021;147(1):9-15. PMID 33180098
  5. Wang H, Li L, Qin LL, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018;3(3):CD004655. PMID 29543316
  6. Markun S, Gravestock I, Jäger L, et al. Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression. Nutrients. 2021;13(3):923. PMID 33809274
  7. House AA, Eliasziw M, Cattran DC, et al. Effect of B-vitamin therapy on progression of diabetic nephropathy: a randomized controlled trial. JAMA. 2010;303(16):1603-1609. PMID 20424250
  8. European Medicines Agency. Article 57 product data (EMA/518502/2018, data as of 9 Oct 2026): Finland lists B12-Vitamiini Ratiopharm (cyanocobalamin, oral use). EMA

Doses are from the source abstracts, read 15 Oct 2026. The cyanocobalamin form of the OB12 product was checked in the full text.

Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.