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A systematic review and meta-analysis of 85 randomized trials found that SGLT2 inhibitor treatment was associated with higher hemoglobin and hematocrit than control treatment. Researchers said the consistent changes may be relevant to anemia management, but whether they improve clinical outcomes or affect clot risk remains uncertain.
A review of 85 randomized trials found that SGLT2 inhibitors were associated with modest increases in hemoglobin and hematocrit across patients with kidney disease, heart failure, type 2 diabetes and cardiovascular disease. The analysis, covering 70,543 participants, was presented at the American Society of Nephrology’s Kidney Week meeting and published in JAMA; its authors said the changes may be relevant to anemia management, but their clinical effects need further study.
Over a median follow-up of 24 weeks, hemoglobin rose by an average of 0.55 grams per deciliter in SGLT2 inhibitor groups and declined by 0.08 g/dL in control groups. The estimated difference between groups was 0.60 g/dL (95% confidence interval 0.55 to 0.66; P<0.001). Hematocrit increased by 2.17% with treatment and fell by 0.13% in control groups, a between-group difference of 2.36 percentage points (95% CI 2.19 to 2.52; P<0.001).
The review also found differences in several related measures. Erythropoietin, a hormone involved in red blood cell production, increased by 2.35 mIU/mL in treatment groups versus 0.04 mIU/mL in controls. Red blood cell concentration rose by 0.23 × 10¹²/L versus 0.02 × 10¹²/L. Ferritin and transferrin saturation fell more in the treatment groups. Changes in hepcidin and serum iron did not reach statistical significance.
The trials evaluated SGLT2 inhibitors alone or added to other treatment. Most studied empagliflozin or dapagliflozin, with other drugs in the class also represented. Participants had a mean age of 62.4 years; 35.9% were female. Average baseline hemoglobin was 13.6 g/dL and hematocrit was 41.5%.
Possible Relevance to Anemia Care
The results add evidence that the rise in hemoglobin and hematocrit occurs across a range of patient groups, rather than appearing only in a single disease population. That consistency may matter because people with chronic kidney disease and heart failure can also experience anemia. The authors said the modest increase could contribute to anemia management, and suggested it may help explain quality-of-life improvements previously reported with SGLT2 inhibitors in some patients. Those possibilities are not proof that the blood-count changes cause better outcomes.
The analysis also bears on how clinicians interpret these laboratory changes. Michele F. Eisenga of University Medical Center Groningen and colleagues reported increases in erythropoietin alongside changes in iron-related measures. They said this pattern points to an effect on red blood cell production and iron metabolism, not merely concentration caused by fluid loss. However, the review does not establish that the changes reduce the need for standard anemia treatments or account for the drugs’ cardiorenal benefits.
The authors also cautioned that people who already have elevated hemoglobin or hematocrit could face potential thromboembolic risk if those levels rise further. The analysis does not establish the size of that risk or show that treatment caused such events. It is a reason to interpret the findings carefully, not evidence for changing medication without clinical guidance.
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How Researchers Interpret the Blood Changes
SGLT2 inhibitors are medicines studied and used across several conditions, including type 2 diabetes, heart failure and chronic kidney disease. Earlier observations linked the drugs to higher hemoglobin and hematocrit. One proposed explanation was hemoconcentration, in which changes in fluid volume make blood components appear more concentrated.
In the report to MedPage Today, Eisenga said the analysis found a consistent pattern that included higher erythropoietin and lower ferritin and transferrin saturation. The researchers also reported post hoc findings suggesting that the hemoglobin difference varied with dose and duration: it reached 0.65 g/dL at 1.5 times the standard clinical dose and 0.71 g/dL at 48 weeks. These analyses do not by themselves establish how those differences affect patients or define an appropriate dose.
In an accompanying editorial, Kai-Uwe Eckardt of Charité-Universitätsmedizin Berlin and Mark J. Koury of Vanderbilt University said the rise in hemoglobin reached its maximum at 48 weeks in the evidence they discussed. They wrote that this timing may fit a gradual change in erythropoiesis feedback better than ongoing volume contraction, while stressing that the available trial data could not confirm the mechanism.
“This is the largest and most comprehensive analysis to date of the effects of SGLT2 inhibitors on hematologic and iron-related parameters.”
— Michele F. Eisenga, MD, PhD, of University Medical Center Groningen, speaking to MedPage Today
Mechanism and Patient Outcomes Remain Open
The review found differences in blood measurements, but it did not establish whether those changes directly improve health outcomes, drive the drugs’ benefits for heart and kidney conditions, or reduce reliance on conventional anemia treatments. Eisenga said future trials need to test those questions.
The mechanism is also unsettled. As Eckardt and Koury noted, the trials provided limited information on red blood cell indices and did not report measurements of red blood cell mass, plasma volume or red blood cell lifespan. Without those measurements, the analysis cannot confirm that higher hemoglobin and hematocrit reflect an increase in red blood cell mass. The possible risk of thromboembolic events among patients with already elevated levels also requires further clarification.
Trials Must Test Clinical Effects
The next step, according to Eisenga, is for clinical trials to assess whether the blood-count changes contribute to cardiorenal benefits or affect the need for established anemia treatments. Further research with direct measurements of red blood cell mass, plasma volume and cell lifespan could help clarify how the changes arise. Until those data are available, the meta-analysis supports an association between SGLT2 inhibitor treatment and higher average hemoglobin and hematocrit, but does not settle what that association means for an individual patient.
Key Questions
How much did hemoglobin change in the analysis?
Hemoglobin increased by an average of 0.55 g/dL in SGLT2 inhibitor groups and decreased by 0.08 g/dL in control groups over a median of 24 weeks. The estimated difference between groups was 0.60 g/dL.
Which patients were included?
The 85 randomized trials included 70,543 participants with chronic kidney disease, heart failure, type 2 diabetes, cardiovascular disease or combinations of these conditions.
Does the study show that SGLT2 inhibitors treat anemia?
No. The analysis found changes in blood and iron-related measures. The authors said those changes may contribute to anemia management, but the review did not establish that the drugs improve anemia outcomes or reduce the need for other treatments.
Why are researchers still studying the mechanism?
The trials did not report direct measurements of red blood cell mass, plasma volume or red blood cell lifespan. Researchers therefore cannot confirm whether the higher hemoglobin and hematocrit reflect increased red blood cell mass, fluid changes or a combination of factors.
Is there a potential safety concern?
The authors cautioned that further increases could potentially raise thromboembolic risk in people whose hemoglobin or hematocrit is already elevated. The analysis did not establish the size of that risk. Patients should discuss treatment and laboratory results with their health care professional.
Source: rss
