Vitamin B12 for Nutritional Deficiency Hair Loss

Q: Does Vitamin B12 help with Nutritional Deficiency Hair Loss?

Based on 19 studies with 8,130 participants, there is insufficient evidence at this time that Vitamin B12 may support Nutritional Deficiency Hair Loss management. Our evidence grade is F (Evidence Against).

Q: How much Vitamin B12 should I take for Nutritional Deficiency Hair Loss?

Studies have used various dosages. A commonly studied range is 2.4 mcg/day. Always consult your healthcare provider before starting any supplement regimen.

Q: Are there side effects of Vitamin B12?

Reported side effects may include Generally well tolerated even at high doses, Rare allergic reactions (itching, swelling), Mild diarrhea or nausea at very high doses. Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.

Q: How strong is the evidence for Vitamin B12 and Nutritional Deficiency Hair Loss?

We rate the evidence as Grade F (Evidence Against). This rating is based on 19 peer-reviewed studies with 8,130 total participants. The overall direction of effect is mixed.

F Not Effective Research shows this is unlikely to be effective for this use.

Based on 19 studies (1 RCT) with 8,130 total participants. Results are mixed across studies.

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The Bottom Line

Research shows mixed results for vitamin B12 and hair loss — while deficiency may contribute to hair thinning, supplementation is unlikely to help unless you have a confirmed B12 deficiency.

Mixed results across 20 studies — no consistent benefit from supplementation
Some studies find lower B12 levels in hair loss patients, others do not
No large-scale RCTs testing B12 supplementation specifically for hair regrowth
Supplementation may only help if a genuine B12 deficiency is present

Key Study Findings

retrospective observational n=113

Telogen Effluvium Following Coronavirus Disease-2019 Infection: A Retrospective Study of 113 Cases.

Dose: None vs: Placebo Effect: None None

Retrospective cohort n=2851

Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience.

Dose: None vs: Placebo Effect: Ferritin low in 46.5% of patients; iron deficiency in 29.5% p<0.05

Review

Medical Marijuana and Treatment Personalization: The Role of Genetics and Epigenetics in Response to THC …

Dose: None vs: None Outcome: None Effect: None None

Population: Review of pharmacogenomics of THC and CBD

case-control study n=180

A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, …

Dose: not applicable vs: Placebo Effect: None None

Cross-Sectional Study n=108

Evaluation of the relationship of digital phototrichogram findings of patients with diffuse hair loss with …

Dose: None vs: Placebo Effect: None 0.05

Case-control n=973

Micronutrient Deficiencies and Digital Computerized Phototrichogram Analysis in Telogen Effluvium: a Retrospective Correlation Study in …

Dose: None vs: Placebo Effect: r=0.417 (HGB and AHR in females) p=0.008

Key Statistics

Studies

8130

Participants

↔

Mixed

Grade

Referenced Papers

Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience. Other

Journal of cosmetic … 2025 4 citations

Medical Marijuana and Treatment Personalization: The Role of Genetics and Epigenetics in Response to THC and CBD. Review

Genes 2025 1 citations

Telogen Effluvium Following Coronavirus Disease-2019 Infection: A Retrospective Study of 113 Cases. Other

International journal of … 2025

A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, vitamin B12, vitamin D, thyroid … Other

Journal of cosmetic … 2024 7 citations

Evaluation of the relationship of digital phototrichogram findings of patients with diffuse hair loss with blood TSH, ferritin and vitamin … Other

Northern clinics of … 2024 1 citations

Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. Other

JAMA 2023 49 citations

Micronutrient Deficiencies and Digital Computerized Phototrichogram Analysis in Telogen Effluvium: a Retrospective Correlation Study in a Tertiary Medical Center. Other

Dermatology practical & … 2023 4 citations

Effects of Cannabidiol on Exercise Physiology and Bioenergetics: A Randomised Controlled Pilot Trial. Other

Sports medicine - … 2022 34 citations

Differentiating Cannabis Products: Drugs, Food, and Supplements. Review

Frontiers in pharmacology 2022 31 citations

Telogen effluvium in daily practice: Patient characteristics, laboratory parameters, and treatment modalities of 3028 patients with telogen effluvium. Other

Journal of cosmetic … 2022 22 citations

Nonscarring scalp alopecia: Which laboratory analysis should we perform on whom? Other

Turkish journal of … 2022 8 citations

CBD Effects on TRPV1 Signaling Pathways in Cultured DRG Neurons. Other

Journal of pain … 2020 56 citations

NonScarring Diffuse Hair Loss in Women: a Clinico-Etiological Study from tertiary care center in North-West India. Observational

Journal of cosmetic … 2019 25 citations

The Role of Micronutrients in Alopecia Areata: A Review. Review

American journal of … 2017 104 citations

Vitamin and Mineral Deficiencies in Patients With Telogen Effluvium: A Retrospective Cross-Sectional Study. Other

Journal of drugs … 2016 56 citations

Clinicoepidemiological Observational Study of Acquired Alopecias in Females Correlating with Anemia and Thyroid Function. Other

Dermatology research and … 2016 26 citations

Trichotillomania: Bizzare Patern of Hair Loss at 11-Year-old Girl. Case Report

Acta dermatovenerologica Croatica … 2016 6 citations

Vitamin B12 and omega-3 fatty acids together regulate lipid metabolism in Wistar rats. Other

Prostaglandins, leukotrienes, and … 2015 40 citations

The role of psychological factors and serum zinc, folate and vitamin B12 levels in the aetiology of trichodynia: a case-control … Other

Clinical and experimental … 2009 34 citations

Management of hair loss in women. Review

Dermatologic clinics 1993 38 citations

Dosage & Usage

mg = milligrams · mcg = micrograms (1,000× smaller) · IU = International Units

Commonly Used Dosages

general:: 2.4 mcg/day
deficiency:: 1,000-2,000 mcg/day

Upper limit: No established UL

Dosages Studied in Research

Dosage	Duration	Effect	N
None	--	Neutral	113
None	--	Neutral	2851
None	--	Mixed	--
not applicable	--	Mixed	180
None	--	Mixed	108
None	--	Positive	973
None	--	Neutral	--
300 mg single dose	--	Mixed	9

Best taken: With meals; sublingual form can be taken any time

Safety & Side Effects

Reported Side Effects

⚠ Generally well tolerated even at high doses
⚠ Rare allergic reactions (itching, swelling)
⚠ Mild diarrhea or nausea at very high doses

Known Interactions

● Metformin (reduces B12 absorption by 10-30%)
● Proton pump inhibitors and H2 blockers (reduce B12 absorption)
● Colchicine (may reduce B12 absorption)

Tolerable upper intake: No established UL

Always consult your healthcare provider before starting any supplement.

Frequently Asked Questions

Does Vitamin B12 help with Nutritional Deficiency Hair Loss?

Based on 19 studies with 8,130 participants, there is insufficient evidence at this time that Vitamin B12 may support Nutritional Deficiency Hair Loss management. Our evidence grade is F (Evidence Against).

How much Vitamin B12 should I take for Nutritional Deficiency Hair Loss?

Studies have used various dosages. A commonly studied range is 2.4 mcg/day. Always consult your healthcare provider before starting any supplement regimen.

Are there side effects of Vitamin B12?

Reported side effects may include Generally well tolerated even at high doses, Rare allergic reactions (itching, swelling), Mild diarrhea or nausea at very high doses. Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.

How strong is the evidence for Vitamin B12 and Nutritional Deficiency Hair Loss?

We rate the evidence as Grade F (Evidence Against). This rating is based on 19 peer-reviewed studies with 8,130 total participants. The overall direction of effect is mixed.

Other ingredients for Nutritional Deficiency Hair Loss

Selenium A Biotin B Vitamin A D L-Cysteine D Folate F

Vitamin B12 for other conditions

Telogen Effluvium F

Quick Verdict

Based on 19 studies (1 RCT) with 8,130 total participants. Results are mixed across studies.

Evidence Strength10%

Low confidence

Study Breakdown

RCT (0)Meta (0)Other (19)

Compare Alternatives

See how other ingredients compare for this condition.

View all ingredients for Nutritional Deficiency Hair Loss

Learn More

References

[1] Ömer Karakoyun et al.. J Cosmet Dermatol. 2025. Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience. doi:10.1111/jocd.70037 PubMed
[2] Małgorzata Kalak et al.. Genes (Basel). 2025. Medical Marijuana and Treatment Personalization: The Role of Genetics and Epigenetics in Response to THC and CBD. doi:10.3390/genes16121487 PubMed
[3] Namrata Chhabra et al.. Int J Trichology. 2025. Telogen Effluvium Following Coronavirus Disease-2019 Infection: A Retrospective Study of 113 Cases. doi:10.4103/ijt.ijt_38_22 PubMed
[4] Irem Nur Durusu Turkoglu et al.. J Cosmet Dermatol. 2024. A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, vitamin B12, vitamin D, thyroid … doi:10.1111/jocd.16512 PubMed
[5] Leyla Bilik et al.. North Clin Istanb. 2024. Evaluation of the relationship of digital phototrichogram findings of patients with diffuse hair loss with blood TSH, ferritin and vitamin … doi:10.14744/nci.2023.33269 PubMed
[6] Pieter A Cohen et al.. JAMA. 2023. Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. doi:10.1001/jama.2023.2296 PubMed
[7] Hakan Arslan et al.. Dermatol Pract Concept. 2023. Micronutrient Deficiencies and Digital Computerized Phototrichogram Analysis in Telogen Effluvium: a Retrospective Correlation Study in a Tertiary Medical Center. doi:10.5826/dpc.1303a202 PubMed
[8] Ayshe Sahinovic et al.. Sports Med Open. 2022. Effects of Cannabidiol on Exercise Physiology and Bioenergetics: A Randomised Controlled Pilot Trial. doi:10.1186/s40798-022-00417-y PubMed
[9] Arash Salehi et al.. Front Pharmacol. 2022. Differentiating Cannabis Products: Drugs, Food, and Supplements. doi:10.3389/fphar.2022.906038 PubMed
[10] Ahu Yorulmaz et al.. J Cosmet Dermatol. 2022. Telogen effluvium in daily practice: Patient characteristics, laboratory parameters, and treatment modalities of 3028 patients with telogen effluvium. doi:10.1111/jocd.14413 PubMed
[11] Ümran Öner et al.. Turk J Med Sci. 2022. Nonscarring scalp alopecia: Which laboratory analysis should we perform on whom? doi:10.3906/sag-2106-28 PubMed
[12] Uma Anand et al.. J Pain Res. 2020. CBD Effects on TRPV1 Signaling Pathways in Cultured DRG Neurons. doi:10.2147/JPR.S258433 PubMed
[13] Kavita Poonia et al.. J Cosmet Dermatol. 2019. NonScarring Diffuse Hair Loss in Women: a Clinico-Etiological Study from tertiary care center in North-West India. doi:10.1111/jocd.12559 PubMed
[14] Jordan M Thompson et al.. Am J Clin Dermatol. 2017. The Role of Micronutrients in Alopecia Areata: A Review. doi:10.1007/s40257-017-0285-x PubMed
[15] Evelyn J Cheung et al.. J Drugs Dermatol. 2016. Vitamin and Mineral Deficiencies in Patients With Telogen Effluvium: A Retrospective Cross-Sectional Study. PubMed
[16] Kirti Deo et al.. Dermatol Res Pract. 2016. Clinicoepidemiological Observational Study of Acquired Alopecias in Females Correlating with Anemia and Thyroid Function. doi:10.1155/2016/6279108 PubMed
[17] Jana Zímová et al.. Acta Dermatovenerol Croat. 2016. Trichotillomania: Bizzare Patern of Hair Loss at 11-Year-old Girl. PubMed
[18] Amrita Khaire et al.. Prostaglandins Leukot Essent Fatty Acids. 2015. Vitamin B12 and omega-3 fatty acids together regulate lipid metabolism in Wistar rats. doi:10.1016/j.plefa.2015.04.006 PubMed
[19] C Durusoy et al.. Clin Exp Dermatol. 2009. The role of psychological factors and serum zinc, folate and vitamin B12 levels in the aetiology of trichodynia: a case-control … doi:10.1111/j.1365-2230.2008.03165.x PubMed
[20] D H Rushton. Dermatol Clin. 1993. Management of hair loss in women. PubMed

FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.