How can an AVM lead to iron & B12 deficiency? PMH: hashimotos thyroid, depression, anxiety, spina bifida occulta (laminectomies in 1983, 2002, and 2003). Levothyroxine, Cytomel, duloxetine, buspirone, trazodone, glycopyralate, and I was taking Valtrex (I had shingles a couple weeks before all this). I went to the ER a few weeks ago because I was having orthostatic palpitations, SOB, and dizziness. I was tachy to 140s when standing. They did a CBC, CMP, CXR, EKG, and gave me 3L NS. The only thing remarkable was hgb 8.7, hct 24.3, RBC 2.5, plates 147, normocytic 94.6, slightly hyperchromic 33.9. I was still symptomatic but DCed home. The next day, I saw my PCP and he admitted me. H&H dropped to 5.9/16.4, RBC 1.7, plates 118, B12 undetectable, folate normal (barely - 7.1), iron 58 (this may have been drawn after 2 units PRBC, I cant remember). Colonoscopy, endoscopy, and small bowel capsule study all unremarkable. Full celiac panel and biopsy neg. Direct Coombs test neg. They did do a smear, and pathology said all was well. Initially my WBC were WNL at 6, but the next day they went down to 3.8. They returned to normal during my hospital stay, but last Wednesday, they were back down to 3.1. No blood in the urine, and I actually don t get a period because I have an IUD. T Bili was normal 0.3, and no jaundice. No new meds except the Valtrex, which I d taken 2 years ago without issue (shingles again). No homocysteine or MMA checked, and the only hemolysis lab they drew was direct Coombs. TSH in the ER was 10, but normal the next day at 4. It s been well controlled since diagnosis. I haven t had to adjust the thyroid meds at all. Fecal occult blood was neg. GI said everything was grossly normal and did not see any evidence of bleeding. I was having headaches (I think they were caffeine withdrawal), but def no seizures and my BP was on the low side (80s/40s-110s/70s). A similar situation happened to me in 2010, but it was a slow depletion because I was tolerating it. Again, colonoscopy, endoscopy, capsule study all neg. I saw a hematologist today and she suggested maybe a ruptured AVM was the culprit and it healed itself already. I’m just confused how an AVM can cause low B12 and iron, but maybe I don’t really understand them that well.