Does Upadacitinib Cause Anemia in Crohn's Disease Patients?
Yes, upadacitinib can cause anemia as a documented adverse effect in patients with Crohn's disease, though it occurs in a minority of patients and is typically mild. 1
Documented Hematologic Effects
The FDA drug label for upadacitinib (Rinvoq) explicitly lists low number of red blood cells (anemia) among the most common side effects in patients treated for Crohn's disease. 1 This is a recognized adverse effect that requires monitoring as part of routine clinical care.
Required Laboratory Monitoring
Mandatory monitoring protocols specifically address anemia risk:
- Complete blood count (CBC) must be checked at baseline, at 1 month, at 3 months, and every 3 months thereafter during upadacitinib therapy. 2
- Hemoglobin decreases ≤20 g/L with levels ≥90 g/L do not require dose adjustment. 2
- Hemoglobin <80 g/L (confirmed by repeat testing) should lead to dose interruption. 2
These specific thresholds indicate that anemia is an anticipated complication requiring systematic surveillance.
Clinical Context and Management
The anemia associated with upadacitinib must be distinguished from other causes common in Crohn's disease:
- Crohn's disease itself frequently causes anemia through chronic inflammation (anemia of chronic disease), iron deficiency from blood loss, and malabsorption. 3
- All IBD patients should undergo minimum anemia workup including CBC with red cell indices, reticulocyte count, serum ferritin, transferrin saturation, and CRP. 3
- The presence of anemia in a Crohn's patient on upadacitinib does not automatically mean the drug caused it—disease activity, iron deficiency, and vitamin B12/folate deficiency must be evaluated. 3
Practical Implications
In real-world cohorts of Crohn's disease patients treated with upadacitinib:
- Safety profiles have been acceptable with anemia not emerging as a major limiting toxicity. 4, 5, 6
- In one prospective real-world study of 105 patients, anemia was not among the most commonly reported adverse events (acne was most common at 22.9%). 5
- Serious adverse events occurred in only 4.5% of patients in another cohort, without anemia being highlighted as a predominant concern. 4
Key Monitoring Pitfall to Avoid
Do not attribute all anemia to upadacitinib without proper workup. Given that Crohn's disease patients have multiple reasons for anemia (active inflammation, iron deficiency from chronic blood loss, vitamin B12 deficiency from ileal disease or resection), a comprehensive evaluation is essential before concluding the JAK inhibitor is the primary cause. 3 The timing of anemia onset relative to drug initiation and response to iron supplementation can help distinguish drug-induced from disease-related anemia.