Pre-Surgery Nutrient Baseline
Normal stomach and small intestine absorb nutrients efficiently.
- 2–5 mg: B12 liver stores (years of reserve)
- 30–300: Normal ferritin (ng/mL range)
- >30: Normal vitamin D (ng/mL sufficient)
- >3: Normal folate (ng/mL sufficient)
Normal absorption physiology
Stomach acid frees B12; intrinsic factor carries it onward.
Duodenum as absorption hub
Iron and calcium absorb mainly in the duodenum.
Reserve buffers deficiency
Body stores delay symptoms even after intake drops.
Anatomic Change After Bariatric Surgery
Surgery reduces acid, intrinsic factor, and bypasses key absorption sites.
- Near-total: Intrinsic factor loss (after RNY bypass)
- Bypassed: Duodenum (main Fe / Ca site)
- ~30 mL: Pouch volume (reduced stomach size)
- Sharply ↓: Acid production (less B12 release)
Stomach pouch reduction
Smaller pouch means less acid to release bound B12.
Intrinsic factor shortfall
Less parietal cell surface makes B12 absorption unreliable.
Duodenal bypass consequences
Iron and calcium skip their primary absorption segment.
Nutrient Decline & Emerging Symptoms
Without supplements, stores deplete and deficiency symptoms surface over months.
- 2–5 yrs: B12 deficiency onset (unsupplemented)
- ~50%: Iron deficiency prevalence (without monitoring)
- ~90%: Vitamin D deficiency (reported prevalence)
- Weeks: Folate deficiency onset (small body stores)
Fatigue and anemia
Low B12 and iron slow red cell production, causing fatigue.
Bone loss risk
Low calcium and vitamin D weaken bone density over time.
Neuropathy warning signs
B12 and folate deficiency can trigger nerve tingling.
Preventing Deficiency With Supplements
A structured regimen replaces what surgery no longer absorbs normally.
- IM / SL: B12 route (monthly or daily)
- 45–60 mg: Elemental iron (per day typical)
- 1200–1500 mg: Calcium citrate (split doses daily)
- 3000 IU: Vitamin D target (per day typical)
B12 injections or sublingual
Bypasses gut absorption limits entirely, restoring levels reliably.
Iron and calcium timing
Calcium and iron are dosed apart to avoid competition.
Daily multivitamin backbone
Bariatric-specific multivitamin covers remaining micronutrient gaps.
Standard supplementation regimen
Routine Lab Monitoring Catches Deficiency Early
Scheduled bloodwork detects dips before they become symptomatic.
- 3,6,12 mo: Lab check schedule (then annually)
- Near-complete: Early correction success (with monitoring)
- Required: Lifelong monitoring (after bariatric surgery)
- Higher: Missed follow-up risk (deficiency rates)
Checkpoint lab schedule
Labs at 3, 6, 12, then annual intervals track trends.
Catching dips early
A falling trend triggers dose adjustment before symptoms.
Lifelong commitment
Monitoring and supplementation continue for the patient's life.