Post-Transplant Erythrocytosis in the SGLT2 Inhibitor Era

Background: Post-transplant erythrocytosis (PTE) occurs in 10–15% of kidney transplant recipients (KTR). Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are increasingly used in nephrology, including transplantation. SGLT2i are known to increase hemoglobin (Hb) and hematocrit (Hct) by hemoconcentration, modulation of iron metabolism and may also rise the erythropoiesis. Methods: A retrospective study was conducted on 140 KTR from a tertiary center in Mexico City (2022–2025). PTE was defined as Hb >17 g/dL or Hct >51%. SGLT2i users were identified simultaneously. Results: Among 140 KTR, 120 met criteria (≥6 months follow-up). PTE occurred in 25 KTR (20.8%), 98% male, median age 33 years (IQR 27–38). Most had deceased donors (68%), and unknown etiology of kidney disease (72%). Median pre-transplant Hb was 11.1 g/dL; 56% received erythropoiesis-stimulating agents. Median altitude of residence was 2250 m, and BMI was 25 kg/m2. All PTE had eGFR >60 ml/min/1.73m2 (median 79.4; IQR 68.4–90.2). Symptoms of hyperviscosity were in 8 (32%); 4 required phlebotomy. Of 120 total KTR, 34 (28.3%) used SGLT2i ≥3 months: 11 in the PTE group (44% of PTE patients) and 23 (68%) in the non-PTE group. In PTE using SGLT2i, mean Hb rose by 1.3 g/dL (p = 0.13). No change was seen in the non-PTE group. There was not association between SGLT2i and PTE (p= 0.18) and the relative risk was 1.74 (95% CI, 0.82-3.56). All KTR received RAAS inhibitors; 5 (20%) were on RAASi pre-transplant, 20 (80%) initiated after PTE diagnosis. Hb declined significantly after RAASi (mean -1.09 ± 0.50 g/dL, p = 0.0378), but this effect was not influenced by SGLT2i use. Conclusion: The PTE rate was higher than reported, predominantly affecting men with preserved graft function. While Hb rose in SGLT2i users with PTE, the increase was not significant, and no effect was seen in non-PTE patients. No association between SGLT2i use and PTE could be confirmed. These findings suggest that SGLT2i may be safely used in transplant patients with elevated Hb/Hct, though further studies are needed.