Should a 75-year-old patient's daily vitamin B12 dosage be decreased given a current level of 1010 pg/mL?

Management of Elevated B12 Levels in a 75-Year-Old on High-Dose Supplementation

You should reduce the daily dose from 1000 mg to 2.4 μg daily (the recommended dietary allowance) or discontinue supplementation entirely if there is no ongoing indication for B12 therapy. 1

Assessment of Current Status

Your patient's B12 level of 1010 pg/mL (approximately 745 pmol/L) is well above the normal range and reflects excessive supplementation rather than a therapeutic need. 1 The current dose of 1000 mg (which I assume you meant as 1000 μg or 1 mg, since 1000 mg would be extraordinarily high) far exceeds any recommended maintenance dose. 1

Key Management Principles

For patients taking high-dose oral B12 supplements (>250-350 μg/day) without a clear indication, the recommendation is to discontinue or reduce to the recommended daily allowance. 1 This is particularly important because:

• The recommended dietary allowance for adults is only 2.4 μg/day 2
• Therapeutic doses for confirmed deficiency range from 1000-2000 μg/day, but only when deficiency is documented 3, 4
• Your patient's elevated level suggests no deficiency exists and the current dose is excessive 1

Specific Dosing Recommendations

If No Indication for Supplementation Exists:

• Discontinue B12 supplementation entirely 1
• Recheck B12 levels in 3-6 months to ensure normalization 1

If There Is a Valid Indication (e.g., malabsorption, pernicious anemia, post-bariatric surgery):

• Reduce to 1000 μg monthly via intramuscular injection rather than daily oral dosing 1, 5
• For patients with normal intrinsic factor, maintenance therapy of 1000 μg IM every 2-3 months is appropriate 5
• Oral maintenance can be 250-350 μg/day if absorption is intact 1

Age-Specific Considerations

At 75 years old, this patient falls into a higher-risk category for B12 deficiency (metabolic B12 deficiency is present in 18.1% of patients over 80 years). 5 However, an elevated level of 1010 pg/mL clearly indicates no deficiency exists. 1

The key question is: Why was this patient started on 1000 μg daily? 3

• If started for documented deficiency that has now been corrected, transition to appropriate maintenance dosing 1
• If started empirically without documented deficiency, discontinue supplementation 1
• If the patient has malabsorption (gastric resection, pernicious anemia, inflammatory bowel disease, chronic PPI use >12 months, metformin use >4 months), continue supplementation but at lower maintenance doses 3, 4

Monitoring Protocol

• Recheck B12 levels in 3-6 months after dose adjustment 1
• Target range is 170-800 pmol/L (approximately 230-1080 pg/mL), with optimal levels around 300-600 pg/mL 6
• If levels remain elevated after discontinuation, this confirms excessive supplementation was the cause 1

Safety Considerations

While B12 is generally considered safe even at high doses (toxicity is rare), there is no benefit to maintaining supraphysiologic levels. 2, 3 The current approach of daily high-dose supplementation without a clear indication represents overtreatment. 1

Common pitfall to avoid: Do not continue high-dose B12 supplementation simply because "it can't hurt." 1 While B12 toxicity is rare, unnecessary supplementation wastes resources and may mask other conditions. 3