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A systematic review and meta-analysis of 85 randomized trials found that SGLT2 inhibitors were associated with higher hemoglobin and hematocrit than control treatments across a range of patient groups. Researchers said the findings may be relevant to anemia management, but the analysis does not establish that the changes improve anemia or explain the drugs’ cardiorenal benefits.
A review of 85 randomized trials found that SGLT2 inhibitors were associated with modest but statistically significant increases in hemoglobin and hematocrit compared with control treatments. The findings, involving 70,543 participants with conditions including chronic kidney disease, heart failure and type 2 diabetes, were presented at the American Society of Nephrology Kidney Week meeting and published in JAMA.
Over a median follow-up of 24 weeks, hemoglobin rose by an average of 0.55 grams per deciliter in SGLT2 inhibitor groups and fell by 0.08 g/dL in control groups. The reported between-group difference was 0.60 g/dL (95% confidence interval 0.55 to 0.66; P<0.001). Hematocrit increased by 2.17% with the drugs and declined 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 analysis also found changes in several measures related to red blood cells and iron. Erythropoietin rose by 2.35 milli-international units per milliliter in treatment groups versus 0.04 in controls, while red blood cell concentration increased by 0.23 × 10¹² per liter versus 0.02. Ferritin fell by 19.78 ng/mL versus 3.08, and transferrin saturation fell by 2.20 percentage points versus 0.10.
Changes in hepcidin and serum iron did not reach statistical significance. The trials included several SGLT2 inhibitors, with empagliflozin and dapagliflozin most commonly studied. The authors also reported post hoc findings suggesting that the size of the hemoglobin difference varied with dose and duration; those analyses do not establish what dose or treatment length should be used for anemia.
Possible Relevance to Anemia Care
The results add evidence that the rise in hemoglobin during SGLT2 inhibitor treatment appears across varied patient groups, rather than in only one disease population. The authors said a modest increase could contribute to anemia management and might help explain quality-of-life improvements previously reported in people with heart failure and chronic kidney disease. Those are proposed explanations, not outcomes established by this analysis.
The pattern of higher erythropoietin alongside lower ferritin and transferrin saturation also suggests that the changes may involve red blood cell production and iron metabolism, not simply a concentration effect from fluid loss. That distinction matters to clinicians interpreting blood tests during treatment. The findings do not, by themselves, support starting an SGLT2 inhibitor solely to raise hemoglobin or replacing established anemia care.
The authors cautioned that people who already have elevated hemoglobin or hematocrit could face a potential increase in thromboembolic risk if those measures rise further. The analysis does not quantify that risk. Treatment decisions remain dependent on a patient’s condition and the medication’s established indications, with individual risks considered by a clinician.
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How the Evidence Was Assembled
The researchers pooled double-blind randomized trials testing SGLT2 inhibitors alone or as add-on treatment. Participants had chronic kidney disease, heart failure, type 2 diabetes, cardiovascular disease, or combinations of those conditions. Their mean age was 62.4 years; 35.9% were female. Average starting hemoglobin was 13.6 g/dL and average hematocrit was 41.5%.
Earlier trial observations had linked these medicines with higher hemoglobin and hematocrit, but researchers had debated whether the effect mainly reflected hemoconcentration, a change in blood concentration associated with fluid balance. In the report, Michele F. Eisenga of University Medical Center Groningen and colleagues pointed to the accompanying erythropoietin and iron-related findings as evidence of a broader biological pattern. The authors did not claim the mechanism was conclusively proven.
An editorial by Kai-Uwe Eckardt of Charité-Universitätsmedizin Berlin and Mark J. Koury of Vanderbilt University Medical Center noted that hemoglobin reached its maximum rise only at 48 weeks in the observations they discussed. They said that timing may fit a gradual adjustment in red blood cell production better than continuing volume contraction. The editorial also stressed that the underlying trials generally lacked measurements needed to determine the mechanism directly.
“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 Clinical Benefit Remain Open
The pooled results establish an average difference in blood measures between trial groups, but they do not show whether the change directly improves anemia symptoms, reduces the need for conventional anemia treatments, or drives the heart and kidney benefits associated with SGLT2 inhibitors. The authors said future trials need to test those questions.
Mechanism is also unresolved. The trials generally did not report direct measures of red blood cell mass, plasma volume or red blood cell lifespan, according to the editorial. Without those data, the relative contributions of red blood cell production and fluid-related concentration cannot be confirmed. The potential for harm among patients with already elevated hemoglobin or hematocrit also requires clearer measurement.
Trials Must Test Patient Outcomes
The next research step is to determine whether the observed blood-count changes translate into meaningful outcomes. Eisenga said future trials should assess whether hematologic shifts directly contribute to cardiorenal benefits or reduce reliance on standard anemia treatments. Studies that track red blood cell mass and related measures could also clarify the biological explanation.
Until such evidence is available, the meta-analysis supports recognition of a consistent laboratory effect, not a new anemia-treatment recommendation. Clinicians and patients will need to interpret the findings alongside each person’s existing diagnosis, blood counts and treatment plan.
Key Questions
How much did hemoglobin increase in the analysis?
Over a median of 24 weeks, hemoglobin rose by an average of 0.55 g/dL in SGLT2 inhibitor groups and fell by 0.08 g/dL in control groups. The reported between-group difference was 0.60 g/dL.
Does this show that SGLT2 inhibitors treat anemia?
No. The analysis found changes in hemoglobin and related measures, but it did not establish that the drugs improve anemia symptoms or replace conventional anemia treatments. The authors said further trials are needed.
What might explain the higher hemoglobin and hematocrit?
The researchers pointed to higher erythropoietin and changes in ferritin and transferrin saturation, which may indicate effects on red blood cell production and iron metabolism. Direct measurements needed to confirm the mechanism were generally unavailable in the trials.
Is a rise in these blood measures always beneficial?
Not necessarily. The authors cautioned that further increases could potentially raise thromboembolic risk in people whose hemoglobin or hematocrit is already elevated. The analysis did not quantify that risk.
Source: rss
