Frequent Urination from Bariatric Multivitamin
Your frequent urination is most likely caused by the high dose of B12 (1000 mcg) in your multivitamin, as excess water-soluble B vitamins are excreted through urine, increasing urinary frequency and volume. This is a benign side effect of B-vitamin supplementation and does not indicate harm.
Why This Occurs
B12 and other B vitamins are water-soluble, meaning your body excretes excess amounts through urine rather than storing them. 1 When you take 1000 mcg of B12 daily—which is the recommended dose for post-sleeve gastrectomy patients—your kidneys filter out what your body doesn't absorb or need, leading to increased urine production and frequency. 1
After sleeve gastrectomy, B12 absorption is impaired due to reduced hydrochloric acid production, but oral supplementation at 1000 mcg daily or 1000 mcg weekly is still effective for most patients. 1 However, much of this dose passes through your system unabsorbed, contributing to increased urination.
What You Should Know About Your B12 Dose
The 1000 mcg B12 dose in your multivitamin is appropriate and necessary after sleeve gastrectomy. 1 Post-bariatric surgery patients require 250-350 mg daily or 1000 mg weekly to prevent deficiency. 1
B12 deficiency after sleeve gastrectomy can develop gradually, as vitamin B12 stores last 2-3 years, and deficiency may present several years after surgery. 1 This is why you need continued supplementation even years post-surgery.
Untreated B12 deficiency can cause irreversible neurological damage, including numbness, tingling, coordination problems, and cognitive difficulties. 1
Common Pitfall to Avoid
Do not reduce or stop your B12 supplementation without medical guidance, even if the frequent urination is bothersome. 1 The neurological consequences of B12 deficiency are serious and potentially irreversible, while frequent urination from excess B vitamins is harmless. 1
Practical Solutions
Try taking your multivitamin earlier in the day rather than evening to minimize nighttime urination, though no specific guideline addresses this timing strategy.
Ensure adequate hydration throughout the day (not just when taking the vitamin) to maintain proper kidney function, as bariatric patients are at risk for dehydration. 1
Have your B12 levels checked at your next follow-up (recommended at 3,6, and 12 months in the first year, then annually). 1 If your levels are consistently very high, your provider might adjust the dosing schedule to weekly rather than daily.
When to Seek Medical Attention
Contact your bariatric team if you experience:
- Excessive thirst beyond what's explained by increased urination
- Signs of dehydration (dark urine, dizziness, dry mouth)
- Pain or burning with urination (suggesting urinary tract infection)
- Blood in urine
- Sudden changes in urination pattern beyond frequency
The frequent urination is likely a harmless side effect of appropriate B12 supplementation, but your bariatric team should verify your B12 levels are in the therapeutic range and rule out other causes like diabetes or urinary tract issues. 1