What is the safe daily intake of Vitamin B6 (Pyridoxine)?

Safe Daily Intake of Vitamin B6

The safe upper limit for vitamin B6 intake is 100 mg per day for adults aged 19-70 years, with sensory neuropathy being the primary adverse effect at higher doses. 1

Recommended vs. Upper Limit Dosages

Daily Requirements

• The Recommended Dietary Allowance (RDA) for vitamin B6 is:
  • 1.3 mg/day for adults aged 14-70 years 1
  • 1.7 mg/day for some adults 1
  • Up to 2 mg/day for pregnant women 1

Upper Limits by Age

• Ages 14-18 years: 80 mg/day 1
• Ages 19-70 years: 100 mg/day 1
• Ages >70 years: 100 mg/day 1

Risk of Toxicity

Vitamin B6 toxicity primarily manifests as peripheral neuropathy with the following considerations:

• High-dose toxicity: Doses >500 mg/day are commonly associated with toxicity 2
• Long-term toxicity: Even doses of 100 mg/day taken long-term can cause spinal cord effects 2
• Recent evidence suggests toxicity can occur at much lower doses:
  • The European Food Safety Authority recently established a more conservative Tolerable Upper Intake Level of 12 mg/day 3
  • Case reports document toxicity at doses as low as 24-40 mg/day, though these may be outliers 4
  • A case report showed toxicity with just 6 mg/day in a multivitamin 5

Clinical Presentation of Toxicity

Vitamin B6 toxicity typically presents as:

• Sensory peripheral neuropathy, predominantly affecting distal regions 2
• Axonal degeneration of sensory nerve fibers 2
• Symptoms may persist even after discontinuation due to slow axonal regeneration 2

Monitoring and Prevention

• Plasma pyridoxal phosphate (PLP) levels can be used to monitor vitamin B6 status:

  • Normal range: 5-50 μg/L or 20-200 nmol/L 2
  • Adequate status: >30 nmol/L (7.4 μg/L) 6
  • Potential for neurotoxicity: >100 nmol/L (25 μg/L) 6

• For supplementation:

  • PLP-based supplements are preferred over pyridoxine due to minimal neurotoxicity 6
  • Weekly administration (50-100 mg) is preferred over daily use to prevent toxicity 6

Special Considerations

• For patients on isoniazid therapy: 25-50 mg/day of pyridoxine is recommended, increasing to 100 mg/day if peripheral neuropathy develops 2
• Elderly patients and those with comorbid conditions may require supplementation to maintain adequate B6 status 6

Management of Toxicity

If toxicity occurs:

1. Immediately discontinue vitamin B6 supplementation 2
2. Provide symptomatic management of neuropathic pain with appropriate medications 2
3. Monitor plasma PLP levels after 4-6 weeks 2
4. Be aware that axonal regeneration takes time and some symptoms may persist 2