---
topic: "Iron, B12 & Malabsorption"
tags: [hematology, iron-deficiency, ferritin, transferrin-saturation, gi-bleeding, oral-iron, b12, homocysteine, celiac, autoimmune-gastritis, malabsorption, vegetarian-diet]
priority: important
last_updated: 2026-05-30
confidence: high
abstract: >-
  This is currently an occult-blood / iron-monitoring / low-normal-B12 problem, not proven
  iron-deficiency anemia or a broad malabsorption syndrome. The completed clean-month blood-side
  summary improved: ferritin rose to 61.60 and TSAT recovered to 33.4%, after the 2026-05-12
  midpoint draw had shown ferritin 43.28 and TSAT 27.7%. The 2026-05-28 stool repeat then turned
  FOB negative with stool RBC absent. Together this supports better iron recovery and a cooled
  occult-blood branch during alcohol/smoking abstinence, without proving the April signal's cause.
  Oral iron and B12 are tools, not diagnostic shortcuts; celiac/autoimmune-gastritis testing stays
  trigger-based.
related_topics:
  - diverticular-disease
  - occult-stool-blood-workup
  - b12-functional-deficiency
  - oral-iron-repletion
  - malabsorption-celiac-autoimmune-gastritis
open_questions:
  - "Do repeat stool blood/direct exam and iron markers stabilize after the clean month?"
  - "Does ferritin drift toward <45-50 ug/L or TSAT stay <20% despite normal CRP?"
  - "Do B12/homocysteine/folate improve with a simple oral B12 trial?"
  - "Can Phnom Penh labs provide tTG-IgA or MMA if trigger thresholds are met?"
---

# Iron, B12 & Malabsorption

## Current conclusion

The current state is **not iron-deficiency anemia**, and not a proven malabsorption syndrome. The useful frame is narrower:
- ferritin previously fell from about 94 to 35 ug/L; late-2025 is now exposure-confounded by likely heavy alcohol/cigarette use, and the next-day 2025-12-23 stool occult blood/RBC test was negative
- April 2026 was different: ferritin was 54.01 with **positive stool occult blood + stool RBCs**, so that round remains the clearer occult-blood signal
- the 2026-05-12 midpoint draw showed ferritin **43.28 ug/L** and TSAT **27.7%** under non-fasting post-meal/coffee conditions; the 2026-05-27 end summary then improved to ferritin **61.60** and TSAT **33.4%** after zero alcohol/smoking
- hemoglobin has remained normal in the available series
- CRP is normal, so ferritin is not obviously being inflated by acute inflammation
- the stool occult blood / stool RBC branch cooled on 2026-05-28 (**FOB negative, stool RBC absent**), but recurrence rules still apply because April 2026 was a real stool-positive signal
- B12 is low-normal and recurrently near the lower range: **231 pmol/L** on 2026-04-19, with prior values 396, 279, 193, 228, 291 pmol/L
- homocysteine has been upper-normal around **10.6-11.9 μmol/L**; folate has historically been adequate
- no current macrocytic anemia signal, but NICE 2024 explicitly says normal hemoglobin/MCV does not rule out B12 deficiency
- old tTG-IgA was negative in 2015; total IgA is high rather than deficient; gastrin was normal in April 2026

Bottom line: repeat trends and source clarification come first. Supplements can run in parallel when justified, but they must not hide whether bleeding or absorption problems persist.

## What changes the decision

| Result / pattern | Interpretation | Action |
|---|---|---|
| Ferritin stable/improving, Hb normal, stool blood clears | Current end-experiment pattern; no active iron-deficiency signal in this snapshot | Monitor / food-first; avoid panic iron loading |
| Ferritin/TSAT improve after abstinence but stool blood is not yet cleared | Iron recovery improved, bleeding-source question unresolved | Keep alcohol/smoking avoidance; complete repeat stool-blood/direct-exam branch rather than declaring bleeding solved |
| Ferritin falls toward <45-50 ug/L, TSAT stays <20%, Hb normal | Non-anemic iron depletion becoming more plausible | Conservative oral iron is reasonable while repeating stool/iron trend |
| Hb starts falling, ferritin drops, stool blood persists | Ongoing loss or mixed process | GI-source escalation matters more than supplement optimization |
| Visible bleeding, melena, rapid weakness, tachycardia/faintness, Hb drop | Higher-risk bleed/anemia branch | Do not manage with supplements; urgent medical/GI evaluation |
| Oral iron worsens bloating/constipation significantly | Repletion may confound gut tracking | Stop, reduce, or switch form/frequency |
| B12 low-normal with brain fog/fatigue/paraesthesia/balance/glossitis/memory symptoms | B12 becomes actionable despite normal CBC | Oral repletion trial plus homocysteine/folate follow-up; clinician review if objective neurologic signs |
| B12 rises but homocysteine stays high | Look beyond B12 | Folate, B6, thyroid, renal function, alcohol relapse, inflammation/gut context; avoid MTHFR rabbit hole unless clinician-directed |
| B12 does not rise on oral dosing | Dose/product/adherence problem or malabsorption | Consider MMA/active B12 if available and trigger-based malabsorption/autoimmune-gastritis branch |
| Persistent iron/TSAT drift, chronic non-bloody diarrhea/steatorrhea, weight loss, refractory aphthae, DH-like rash, or persistent unexplained bloating with objective markers | Celiac/malabsorption becomes actionable | tTG-IgA while eating gluten; GI confirmation if positive/high |
| Poor B12/iron response, rising gastrin, upper-GI features, or gastroscopy already indicated | Autoimmune/atrophic gastritis branch becomes relevant | Intrinsic-factor Ab first for specificity, parietal-cell Ab for sensitivity if available; biopsy distribution matters if scoped |

## What to do now

1. If stool follow-up is not already done, repeat the useful trend set rather than chasing isolated serum iron: CBC with indices/RDW, ferritin, serum iron, TIBC or transferrin, TSAT, CRP, and stool-blood/direct-exam follow-up as owned by [GI Bleeding / Diverticular / Stool Blood](#sec-diverticular).
2. Do not make oral iron automatic from the April snapshot. If ferritin/TSAT drift again or symptoms justify repletion, use a conservative regimen:
   - ferrous bisglycinate if available/tolerated; otherwise sulfate/fumarate/gluconate are acceptable but often harsher
   - **25-36 mg elemental iron every other day** to start; consider 45-65 mg only if response is poor and tolerated
   - morning empty stomach if tolerated, otherwise with a small non-calcium snack
   - optional vitamin C / fruit support
   - separate from coffee/tea, calcium, magnesium, zinc, high-fiber supplements, antacids/PPIs if avoidable, and psyllium by about 2 hours or more
   - reassess ferritin/TSAT/Hb after **6-8 weeks**
3. Define oral-iron success before starting:
   - ferritin rises about 10-30 ug/L, TSAT improves, Hb stable = useful repletion response
   - ferritin rises but stool blood persists = tablets are repleting, but source branch remains active
   - no ferritin/TSAT response = ongoing loss, poor adherence/timing, malabsorption, wrong dose/form, or inflammation/sequestration
   - Hb falls despite iron = escalate
4. B12: because diet is vegetarian-leaning and B12 is repeatedly low-normal, simple oral support is reasonable without a large panel:
   - no clear neurologic symptoms: 1000 mcg cyanocobalamin or methylcobalamin 2-3x/week, or 250-500 mcg/day
   - compatible symptoms: 1000 mcg/day for 8-12 weeks, then step down if symptoms/labs improve
   - recheck B12 + homocysteine + folate in 8-12 weeks if this becomes an active experiment
   - MMA is useful only if accessible or symptoms persist despite adequate oral B12
5. Malabsorption/celiac: do not automatically add a broad panel. If triggered, ask for the exact test **tTG-IgA / anti-TG2 IgA while eating gluten**. Add total IgA only if the lab requires same-day pairing; IgA deficiency is already ruled out by elevated total IgA.
6. Autoimmune gastritis/pernicious branch: do not shotgun now. Trigger only if B12/iron behavior worsens or fails to respond, gastrin rises, upper-GI symptoms appear, or gastroscopy is being done anyway. If scoped, ask for gastric body + antrum/incisura biopsies in separately labelled jars plus H. pylori assessment.

Local availability reminders:

| Test | Biomed public status / price | Use |
|---|---:|---|
| B12 | listed, $17.50 | repeat only if tracking response |
| Folate | listed, $16.25 | interpret homocysteine |
| Homocysteine | listed, $25 | best local functional proxy if MMA unavailable |
| MMA / active B12 | not listed | do not assume availability |
| Total IgA | listed, $10 | already high; not needed solely to validate tTG |
| tTG-IgA / anti-TG2 IgA | not listed publicly | ask exact off-menu/send-out wording or another hospital/lab |
| DGP/EMA/HLA-DQ2/DQ8 | not listed publicly | second-line only; HLA-B27 is not a celiac HLA test |
| Gastrin | listed, $19.50; already normal April 2026 | repeat only if suspicion changes |
| H. pylori stool antigen | listed, $15; prior negative Dec 2025 | repeat only with upper-GI/iron-loss trigger or clinician request |

## What not to do

- Do not let iron supplementation make the diagnostic branch disappear. A ferritin bump from tablets does not prove bleeding stopped.
- Do not treat black/dark stool on oral iron as proof of bleeding; also do not dismiss visible blood or positive FOB as “just the iron” without clinical/lab context.
- Do not delay stool-blood/GI-source workup because oral iron is possible.
- Do not run a broad autoimmune/malabsorption panel for bloating alone.
- Do not self-diagnose celiac by going gluten-free before testing; negative serology after gluten restriction is unreliable.
- Do not substitute HLA-B27 or generic IgA/IgG tests for celiac-specific testing.
- Do not use B12 injections by default; reserve clinician/IM-route logic for objective neurologic signs, poor oral response, or strong malabsorption/pernicious concern.
- Do not add high-dose B6 casually; chronic excess can cause neuropathy and muddy symptom interpretation.
- Do not use IV iron as default. It becomes a clinician discussion if oral iron is not tolerated, ferritin/TSAT fail to respond after 6-8 weeks with good adherence/timing, Hb declines/symptomatic anemia develops, or malabsorption/ongoing loss makes oral repletion unrealistic.

## Evidence and owner links

- Current owner: [Iron, B12 & Malabsorption](#sec-ferritin).
- Absorbed detail covered here: oral iron, celiac/autoimmune-gastritis screening, and B12 follow-up.

Evidence anchors retained from the absorbed pages:

- Iron deficiency / GI evaluation: AGA IDA guideline PMID: 32810434; BSG IDA guideline PMID: 34497146; AGA Clinical Practice Update on IDA PMID: 38864796; non-anaemic iron deficiency review PMID: 34908363; serum iron variability PMID: 12090432.
- Oral iron dosing/tolerability: hepcidin physiology PMID: 26289639; alternate-day absorption PMID: 31413088; alternate-day RCT PMID: 36725875; daily-vs-alternate systematic review PMID: 37979057.
- B12 framework: NICE NG239 (2024), Vitamin B12 deficiency in over 16s: diagnosis and management, https://www.nice.org.uk/guidance/ng239.
- Adult celiac diagnosis: ESsCD 2025 guideline PMID: 40999951; ACG 2023 guideline update PMID: 36602836.
- Autoimmune/atrophic gastritis: AGA atrophic gastritis clinical practice update PMID: 34454714; autoimmune gastritis clinical management review PMID: 34484423; corpus-restricted atrophic gastritis biomarker study PMID: 36428844.

This is the canonical iron/B12/malabsorption owner. Oral iron, B12, celiac, and autoimmune-gastritis decisions should be read here rather than as separate pages.