Low hemoglobin in older adults is common and becomes more likely with each decade of life. Among adults 65 to 74, roughly 7 to 8 percent are anemic. By age 85 and older, that number jumps to about 40 percent in men and 22 percent in women. The causes range from nutritional gaps and chronic diseases to slow blood loss and changes in the bone marrow itself, and in many cases more than one factor is at work simultaneously.
Anemia is defined as hemoglobin below 13 g/dL in men and below 12 g/dL in women. Even mild drops below these thresholds carry real consequences for older adults: both low and high hemoglobin levels are linked to increased dementia risk in a U-shaped pattern, with anemia specifically associated with a 34 percent higher risk of dementia and a 41 percent higher risk of Alzheimer’s disease. Falls, fatigue, and declining physical function all become more likely as hemoglobin drops.
Iron Deficiency and Blood Loss
Iron deficiency is one of the most frequent causes of low hemoglobin in seniors, and it almost always points to chronic blood loss somewhere in the digestive tract rather than simply not eating enough iron-rich food. Peptic ulcers are the most common source of upper GI bleeding. These open sores develop on the stomach lining or upper small intestine, often triggered by regular use of anti-inflammatory painkillers like ibuprofen or aspirin. Many older adults take these medications daily for arthritis or heart protection, creating a slow, steady leak of blood they may never notice.
In the lower digestive tract, colon polyps, diverticular disease, and abnormal blood vessel formations called angiodysplasia can all cause small amounts of bleeding over weeks or months. Colorectal cancer is another important cause. Because the blood loss is often invisible to the naked eye, hemoglobin can drop gradually before any obvious symptoms appear. This is why unexplained iron deficiency in an older adult typically prompts a closer look at the GI tract.
Vitamin B12 and Folate Deficiency
Vitamin B12 deficiency in older adults is rarely about diet. The real problem is absorption. As people age, the stomach lining thins and produces less acid and less of a protein called intrinsic factor, both of which are needed to pull B12 from food. In pernicious anemia, the immune system attacks the stomach cells that make intrinsic factor, effectively blocking B12 uptake regardless of how much meat, dairy, or fortified food a person eats. People who have had stomach surgery face a similar problem, with 10 to 30 percent of those with a partial gastrectomy developing inadequate B12 absorption.
Folate deficiency works differently. It genuinely is a dietary issue. Older adults who eat few vegetables, fruits, or fortified grains, or who have poor appetites due to illness or medication side effects, can become deficient. Both B12 and folate are essential for producing healthy red blood cells, and a shortage of either one leads to abnormally large, poorly functioning cells that carry less oxygen.
Chronic Inflammation
One of the trickiest causes of low hemoglobin in older adults is sometimes called “anemia of inflammation” or “anemia of chronic disease.” Conditions like rheumatoid arthritis, heart failure, chronic infections, and even obesity keep the immune system in a state of low-grade activation. This ongoing inflammation triggers a chain reaction that starves the body of usable iron, even when iron stores are technically adequate.
Here’s how it works: inflammatory signals, particularly a molecule called IL-6, tell the liver to ramp up production of a hormone called hepcidin. Hepcidin acts like a gatekeeper. It blocks iron absorption in the gut and traps iron inside immune cells, preventing it from reaching the bone marrow where red blood cells are made. The result is that serum iron drops quickly, even though the body has iron locked away in storage. Standard iron supplements often don’t help much because the absorption pathway is shut down.
Inflammation also directly interferes with the production of red blood cells in another way. Inflammatory molecules suppress the kidneys’ ability to produce a hormone that signals the bone marrow to make more red blood cells. They can also make the bone marrow less responsive to that signal and shorten the lifespan of existing red blood cells. This double hit, less iron reaching the marrow and weaker signals telling it to produce cells, explains why anemia of inflammation can be stubborn and hard to correct without addressing the underlying condition.
Kidney Disease
The kidneys play a central role in red blood cell production that most people don’t realize. When kidneys are healthy, they sense low oxygen levels in the blood and respond by producing a hormone (EPO) that tells the bone marrow to make more red blood cells. As kidney function declines, and it does gradually in many people over 65, this hormonal signal weakens. The bone marrow simply doesn’t get the message to produce enough cells.
Kidney-related anemia typically becomes significant when kidney function drops below about 30 percent of normal capacity. Since chronic kidney disease often develops silently over years, the anemia it causes can creep up without a clear trigger. Diabetes and high blood pressure, both extremely common in older adults, are the leading drivers of kidney damage.
Bone Marrow Disorders
When anemia in an older adult can’t be explained by nutritional deficiencies, inflammation, kidney disease, or blood loss, the bone marrow itself may be the problem. Myelodysplastic syndromes (MDS) are a group of conditions where the bone marrow produces defective blood cells. The incidence rises sharply with age, exceeding 20 cases per 100,000 people per year in older populations. Among those diagnosed, 93 percent are anemic at the time of diagnosis.
MDS should be suspected when anemia comes with certain warning signs: red blood cells that are larger than normal, drops in other blood cell types (white cells or platelets), or hemoglobin that falls below 9 g/dL without a clear explanation. A bone marrow biopsy is typically needed to confirm the diagnosis. Other marrow-related causes include blood cancers like leukemia or lymphoma, though these are less common.
Medications That Lower Hemoglobin
Several drug classes commonly prescribed to older adults can contribute to low hemoglobin through different mechanisms. NSAIDs like ibuprofen and aspirin cause GI bleeding directly. Anticoagulants (blood thinners) amplify bleeding risk throughout the body. Proton pump inhibitors, widely used for acid reflux, can impair iron and B12 absorption over time by reducing stomach acid.
Some medications trigger a rarer form of anemia where the immune system mistakenly attacks red blood cells. Certain antibiotics, particularly cephalosporins, are the most common culprits. Penicillin derivatives, some Parkinson’s medications, and even NSAIDs can occasionally cause this immune-mediated destruction. Because older adults often take multiple medications simultaneously, drug-related anemia is worth considering whenever hemoglobin drops without an obvious explanation.
How These Causes Are Identified
Sorting out the cause of low hemoglobin in an older adult usually starts with a complete blood count and a look at the size and shape of red blood cells under a microscope. From there, iron levels, B12, folate, kidney function, thyroid function, and markers of inflammation are checked. The pattern of results points toward the likely cause.
Iron deficiency, for instance, shows up as low iron stores (ferritin below 50 ng/mL). Anemia of inflammation looks superficially similar, with low circulating iron, but iron stores are actually elevated because the body is hoarding iron rather than lacking it. B12 deficiency typically produces unusually large red blood cells. Kidney-related anemia correlates with low kidney filtration rates. In many older adults, two or three of these problems overlap, making the picture more complex than it would be in a younger person.
For mild, stable anemia, blood work alone is usually sufficient. A bone marrow biopsy is reserved for cases with red flags: large red blood cells, drops in multiple blood cell types, hemoglobin below 9 g/dL, or anemia that keeps worsening without a clear reason.