What vitamin deficiency can cause brittle nails that split down the middle?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: June 22, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Biotin deficiency is the most likely cause of brittle nails that split down the middle, and supplementation with biotin is recommended to address this issue. According to a review published in the American Journal of Clinical Dermatology in 2017 1, biotin supplementation has been successful in the treatment of brittle nails, also known as onychoschisis.

Key Points to Consider

  • Biotin is an important coenzyme for carboxylation reactions and plays a crucial role in keratin production, which is essential for healthy nail growth.
  • The recommended daily intake of biotin for healthy nail growth is not established, but studies have used doses of 20 mg per day, as seen in the study by Camacho et al. mentioned in the review 1.
  • Foods rich in biotin, such as eggs, nuts, seeds, salmon, and avocados, can help increase biotin intake, but supplementation may be necessary to achieve optimal levels.
  • It is essential to note that nail growth is slow, and improvement may take time, typically 3-6 months, before noticeable results are seen.
  • While biotin supplementation is generally well-tolerated, it is crucial to consult a healthcare provider if nail problems persist, as other underlying conditions, such as thyroid disorders, iron deficiency, or fungal infections, may be contributing factors.

From the Research

Vitamin Deficiency and Brittle Nails

  • Brittle nails that split down the middle can be caused by a deficiency in certain vitamins, particularly biotin, also known as vitamin B7 2, 3, 4, 5, 6.
  • Biotin plays a crucial role in maintaining nail health, and its deficiency can lead to brittle nails, onychoschizia, and onychorrhexis 2, 4.
  • Studies have shown that oral supplementation with biotin can improve nail strength and reduce brittleness in patients with brittle nail syndrome 2, 3, 4, 5, 6.
  • The recommended daily dose of biotin for improving nail health is 2.5-10 mg per day 4, 5, 6.
  • While other vitamins and minerals, such as vitamin E, vitamin C, and zinc, may also be important for nail health, the evidence suggests that biotin is the most effective supplement for treating brittle nails 4.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Brittle nails.

Journal of cosmetic dermatology, 2004

Research

Vitamins and minerals: their role in nail health and disease.

Journal of drugs in dermatology : JDD, 2007

Research

[Treatment of brittle fingernails with biotin].

Zeitschrift fur Hautkrankheiten, 1989

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.