Can Low Testosterone Cause Anemia? What the Testosterone Trials and TRAVERSE Showed in Men Over 40

Low testosterone and anemia show up together more often than chance would predict in older men. In the Testosterone Trials, 58.3% of men with unexplained anemia were no longer anemic after a year of testosterone gel, against 22.2% on placebo, and the much larger TRAVERSE study found a smaller but consistent benefit.

Can low testosterone cause anemia? Low testosterone is linked to anemia in older men, and placebo-controlled trials show that raising testosterone back to normal corrects the anemia in a meaningful share of them. Testosterone deficiency causes mild anemia, according to the authors of the TRAVERSE anemia study published in JAMA Network Open in 2023. The effect is usually modest, but in a man whose hemoglobin is already borderline it can be the difference between a normal blood count and a flagged one.

The question matters because anemia in older men often has no obvious explanation. In one-third of older men with anemia, no recognized cause can be found, according to Roy and colleagues writing in JAMA Internal Medicine in 2017. This guide covers how testosterone drives red blood cell production, what the observational and randomized evidence shows about low testosterone anemia, why iron status changes the response, and where the overshoot risk begins. Every figure comes from studies opened and checked for this article.

Testosterone raises red blood cell production by boosting erythropoietin, the kidney hormone that tells bone marrow to make red cells, and by freeing up iron for new cells. Bachman and colleagues showed this in older men with mobility limitation who were randomized to testosterone gel or placebo for 6 months, published in the Journals of Gerontology in 2014. Hemoglobin and hematocrit rose 7%-10% on testosterone, alongside higher erythropoietin and lower hepcidin and ferritin at 1 and 3 months.

Hepcidin is the liver hormone that locks iron away in storage. When testosterone suppresses hepcidin, more iron reaches the bone marrow. The Bachman team proposed that testosterone recalibrates the erythropoietin set point, so the body aims for a higher hemoglobin level than it would with low testosterone. That set point idea explains both sides of the story: a lift for men who are low, and an overshoot risk for men who are already normal.

Yes. Older men with the lowest testosterone are several times more likely to be anemic than men with the highest. The InCHIANTI study, led by Ferrucci and published in the Archives of Internal Medicine in 2006, measured testosterone and hemoglobin in 905 people aged 65 or older in Italy, excluding anyone with cancer, kidney failure or anti-androgen treatment.

The InCHIANTI researchers also followed people who started without anemia and rechecked hemoglobin after 3 years. Men and women with low total testosterone had a relative risk of 2.1 for developing anemia, and those with low bioavailable testosterone had a relative risk of 3.9. Observational data like these cannot prove that low testosterone causes anemia, which is why the randomized trials below matter. If you are unsure which testosterone number your lab report shows, our guide to free versus bioavailable testosterone explains the difference.

In the Testosterone Trials, a year of testosterone gel corrected unexplained anemia in most of the men who had it. The Anemia Trial, led by Roy and colleagues, drew on 788 men aged 65 or older with average testosterone below 275 ng/dL at 12 academic medical centers in the United States. Of those men, 126 were anemic, defined as hemoglobin of 12.7 g/dL or lower, and 62 had no known cause. Their mean age was 74.8.

After 12 months, 58.3% of testosterone-treated men with unexplained anemia were no longer anemic, compared with 22.2% on placebo. Hemoglobin rose by 1.0 g/dL or more in 54% of the testosterone group versus 15% on placebo. Men whose anemia had a known cause, such as iron deficiency, also responded: 52% reached the 1.0 g/dL rise on testosterone versus 19% on placebo.

The Roy authors were careful about what the numbers prove. They wrote that the overall health benefits remain to be established, meaning the trial showed better blood counts, not fewer falls, hospital stays or deaths. They did suggest that testosterone might be measured in men 65 or older who have unexplained anemia and symptoms of low testosterone.

The TRAVERSE anemia study confirmed the benefit in a far larger and younger group, though the gap between testosterone and placebo was smaller. Pencina and colleagues nested the study inside TRAVERSE, the cardiovascular safety trial of testosterone, and enrolled 5204 men aged 45 to 80 at 316 US sites. Every man had 2 testosterone results below 300 ng/dL, symptoms of hypogonadism, and heart disease or raised heart risk. Men were randomized to 1.62% testosterone gel or placebo gel daily.

Of the 5204 men, 815 had anemia at the start, defined as hemoglobin below 12.7 g/dL, and 4379 did not. Anemia corrected in a greater share of testosterone-treated men at every checkpoint: 41.0% versus 27.5% at 6 months, 45.0% versus 33.9% at 12 months, and 42.8% versus 30.9% at 24 months. By 48 months the figures were 44.6% and 39.2%, with far fewer men still in follow-up.

Two further findings stand out. Among men who were not anemic at the start, a smaller proportion of testosterone-treated men developed anemia than men on placebo. And changes in hemoglobin were associated with changes in energy level, which suggests that some of the tiredness men attribute to low testosterone may run through the blood count. The anemic group was also notably different: 30.3% were Black, compared with 14.4% of men without anemia.

Testosterone needs iron to build red cells, so a man who is short on iron gets a weaker and less predictable hemoglobin rise. Artz and colleagues looked at 95 anemic men from the Testosterone Trials in the Journal of Clinical Endocrinology and Metabolism in 2020, splitting them into 58 men with unexplained anemia and 37 with iron deficiency anemia.

In the men with unexplained anemia, testosterone raised hemoglobin by 0.58 g/dL more than placebo and suppressed hepcidin by 8.2 ng/mL and ferritin by 19.6 µg/L, a sign that stored iron was being pulled into new red cells. In the iron-deficient men, hemoglobin rose by 0.38 g/dL, a result that was more variable and not statistically significant. The authors concluded that the effect appears to be attenuated by iron deficiency.

The practical point is that testosterone is not a substitute for finding and fixing iron loss. Iron deficiency in an adult man always needs an explanation, and our article on ferritin and testosterone covers how iron stores and hormones interact.

Yes. The same effect that corrects anemia can push hemoglobin too high in men who started with a normal count. In the Testosterone Trials, testosterone pushed hemoglobin above 17.5 g/dL in 6 men who had not been anemic at baseline. Across 51 studies pooled by Fernandez-Balsells and colleagues in the Journal of Clinical Endocrinology and Metabolism in 2010, testosterone raised hemoglobin by an average of 0.80 g/dl and hematocrit by 3.18%.

The Endocrine Society guideline from 2018 recommends against starting testosterone in men with elevated hematocrit and calls for measuring testosterone and hematocrit during the first year of therapy. Our guide to hematocrit on TRT explains what happens when the count climbs and how clinicians respond.

A man with anemia that has no clear cause, especially if he also has symptoms such as low libido or fatigue, has a reasonable case for asking about testosterone. The Roy authors suggested this for men 65 or older with unexplained anemia and low testosterone symptoms. Anemia from bleeding, kidney disease, vitamin deficiency or bone marrow disease still needs its own workup first, because a low testosterone result does not rule those out.

The Endocrine Society guideline recommends diagnosing hypogonadism only with symptoms plus repeated morning fasting total testosterone results that are unequivocally low. A single afternoon reading is not enough. Our guide to testing testosterone accurately covers the timing and fasting rules.

This article is for educational purposes only and is not medical advice. It does not diagnose, treat, cure or prevent any disease. Speak with a doctor about any abnormal blood count or before starting testosterone therapy.

• Pencina KM et al. Efficacy of Testosterone Replacement Therapy in Correcting Anemia in Men With Hypogonadism: A Randomized Clinical Trial. JAMA Network Open, 2023. https://doi.org/10.1001/jamanetworkopen.2023.40030
• Roy CN et al. Association of Testosterone Levels With Anemia in Older Men: A Controlled Clinical Trial. JAMA Internal Medicine, 2017. https://doi.org/10.1001/jamainternmed.2016.9540
• Ferrucci L et al. Low testosterone levels and the risk of anemia in older men and women. Archives of Internal Medicine, 2006. https://doi.org/10.1001/archinte.166.13.1380
• Artz AS et al. Markers of Iron Flux during Testosterone-Mediated Erythropoiesis in Older Men with Unexplained or Iron-Deficiency Anemia. Journal of Clinical Endocrinology and Metabolism, 2020. https://doi.org/10.1210/clinem/dgaa521
• Bachman E et al. Testosterone induces erythrocytosis via increased erythropoietin and suppressed hepcidin: evidence for a new erythropoietin/hemoglobin set point. Journals of Gerontology Series A, 2014. https://doi.org/10.1093/gerona/glt154
• Fernandez-Balsells MM et al. Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. Journal of Clinical Endocrinology and Metabolism, 2010. https://doi.org/10.1210/jc.2009-2575
• Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology and Metabolism, 2018. https://doi.org/10.1210/jc.2018-00229

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