Anemia before hip or knee replacement: why hemoglobin matters

Low hemoglobin does not automatically rule out hip or knee replacement. It does deserve attention because anemia is associated with a higher likelihood of transfusion, longer hospital stays, readmission, and complications after total joint arthroplasty. The safest response is to identify the cause early, treat what is reasonably correctable, and decide whether surgery should proceed or wait based on the whole clinical picture.

Anemia is a laboratory finding, not a complete diagnosis. Iron deficiency is common, but blood loss, kidney disease, inflammation, vitamin B12 or folate deficiency, bone-marrow disorders, and some medicines can also lower hemoglobin. Taking iron without knowing the cause can delay the right diagnosis and may not help.

Hemoglobin is the protein in red blood cells that carries oxygen. Joint replacement causes some blood loss even when modern blood-conservation techniques are used. A patient who starts with fewer red blood cells has less reserve if the hemoglobin falls after surgery.

The number matters, but so do symptoms, the trend over time, heart or lung disease, kidney function, active bleeding, the expected complexity of surgery, and the ability to recover. A stable person with mild anemia is different from someone with rapidly falling hemoglobin, chest symptoms, black stool, or severe fatigue.

Preoperative anemia is not rare in adults having joint replacement. In a cohort of 15,222 total joint arthroplasty patients, about one in five met the study definition of anemia. Those patients received transfusions more often and had longer hospital stays. Periprosthetic joint infection was also more frequent, although an observational study cannot prove that anemia alone caused each infection.

A later systematic review pooling more than 1.4 million hip and knee replacement patients found associations between preoperative anemia and multiple adverse outcomes, including readmission and wound, cardiac, respiratory, renal, and infectious complications. The studies used different definitions and had substantial heterogeneity, so the results describe population-level risk rather than predicting one person's outcome.

Mild anemia may cause no obvious symptoms. When symptoms occur, they can include fatigue, reduced exercise tolerance, shortness of breath with activity, dizziness, headache, a rapid heartbeat, pale skin, or feeling unusually cold. These symptoms overlap with many other conditions, and severe arthritis itself can limit activity enough to hide reduced endurance.

A complete blood count is the usual starting point. The hemoglobin value, red-cell size, and other indices can suggest a direction, but they do not always reveal the cause. Comparing current results with prior tests is often more useful than looking at one isolated number.

International surgical-anemia guidance recommends evaluating the cause whenever possible early enough for treatment to work. The history should include prior anemia, blood donation or transfusion, gastrointestinal or menstrual blood loss, diet, kidney disease, inflammatory conditions, cancer treatment, bariatric or intestinal surgery, and medicines that affect bleeding or absorption.

Depending on the pattern, testing may include ferritin, serum iron, transferrin saturation, kidney function, vitamin B12, folate, reticulocyte count, and other studies. Iron deficiency should prompt a search for why iron is being lost or not absorbed. In an adult, unexplained iron deficiency should not be assumed to come from poor diet without appropriate medical evaluation.

Iron is necessary to make hemoglobin. If testing confirms iron deficiency, treatment may involve oral or intravenous iron, together with evaluation of the source. Oral iron is inexpensive and convenient but may take weeks to months, can cause nausea or constipation, and may be poorly absorbed. Intravenous iron works differently and may be considered when time is short, oral iron is not tolerated or absorbed, or the deficiency is substantial.

Iron can be inappropriate when anemia has another cause or iron stores are already adequate. Do not start high-dose iron solely because a hemoglobin result is low. A clinician should interpret the blood count and iron studies together, especially when inflammation or chronic disease can alter ferritin.

Vitamin B12 and folate are needed for normal red-cell production. Deficiency can follow dietary restriction, malabsorption, stomach or intestinal surgery, and some medicines. Kidney disease can reduce erythropoietin, a hormone that stimulates red-cell production. Chronic inflammation may limit how the body uses stored iron.

Treatment should match the cause. That may mean replacing a vitamin, treating iron deficiency, addressing bleeding, adjusting a medication, managing kidney-related anemia, or involving primary care, gastroenterology, hematology, nephrology, or another specialist. Erythropoiesis-stimulating medicines are used selectively because they have indications, risks, timing requirements, and cost considerations.

The best time is early in surgical planning, not the week before the operation. Consensus guidance favors beginning evaluation as soon as surgery is scheduled and, when possible, several weeks in advance. More time allows oral treatment to work, permits follow-up testing, and provides room to investigate blood loss or another condition without creating a last-minute cancellation.

A short timeline does not mean evaluation is pointless. Some treatments act faster than others, and the result may still guide anesthesia, blood-management, or postoperative planning. The practical question is what can change safely before the planned date and whether that change is likely to improve the balance of risk and benefit.

A prospective comparative study of an elective hip and knee arthroplasty program found that algorithm-based anemia screening and management was associated with fewer transfusions, fewer readmissions, fewer critical-care admissions, and a shorter hospital stay. Because the study compared care before and after a program change, it supports the value of a structured pathway but does not prove that one treatment explains every improvement.

A systematic review of preoperative iron treatment in anemic hip and knee replacement patients found fewer transfusions and shorter stays among treated patients. Most included studies were not randomized, so the authors emphasized that higher-quality trials were still needed. The lesson is to use diagnosis-led treatment, not to promise that iron will eliminate transfusion.

Patients sometimes hear that transfusion is considered only below a certain hemoglobin level and assume any value above that is safe for elective surgery. These are different decisions. The 2023 AABB guidelines support a generally restrictive transfusion approach for stable hospitalized adults and note that clinicians may use a threshold around 8 g/dL in orthopedic surgery, while considering symptoms and the clinical context.

That guidance addresses when transfused red blood cells may be appropriate—not what hemoglobin should be accepted weeks before elective joint replacement. Preoperative readiness depends on cause, trend, symptoms, expected blood loss, medical conditions, and whether treatment is likely to help.

Sometimes a delay is reasonable, but it should have a purpose. Surgery may need to wait when anemia is severe, symptomatic, rapidly worsening, caused by active bleeding, unexplained, or likely to improve meaningfully with treatment. A new anemia can also reveal a medical problem that matters more urgently than the arthritic joint.

In other situations, proceeding with an adapted plan may be appropriate because the anemia is mild and stable, the cause is understood, treatment has begun, or delaying surgery would create greater harm from pain, immobility, falls, and deconditioning. If a delay is recommended, ask for a specific plan: what diagnosis is being evaluated, what treatment is planned, what result will be rechecked, and who decides when surgery can proceed.

Patient blood management starts before the operating room. It can include treating anemia, reviewing medicines and supplements that affect bleeding, planning tranexamic acid when appropriate, using efficient surgical technique, minimizing unnecessary blood draws, maintaining body temperature, and applying evidence-based transfusion decisions.

Do not stop aspirin, anticoagulants, anti-inflammatory medicine, vitamins, or supplements without instructions. The correct plan depends on why you take them and the bleeding and clotting risks in your case. Review the complete medication list with the surgical and anesthesia teams.

Protein, iron, vitamin B12, folate, and adequate calories support blood-cell production and healing. Food sources can be part of the plan, but diet alone may not correct substantial deficiency before surgery, and anemia from kidney disease, inflammation, marrow disease, or ongoing blood loss requires more than nutrition advice.

The JRH surgical nutrition guide can help organize protein and recovery nutrition. Pair it with the cause-specific medical plan rather than using supplements as a substitute for testing.

Bring information that helps the team see the trend and identify the cause:

Contact a clinician promptly for a new or worsening anemia, black or bloody stool, vomiting blood, heavy bleeding, increasing shortness of breath, marked weakness, fainting, a rapid or irregular heartbeat, or symptoms that are progressing. Call 911 for chest pain, severe trouble breathing, fainting with ongoing symptoms, signs of stroke, or uncontrolled bleeding.

After joint replacement, fatigue and a temporary hemoglobin drop can occur, but worsening dizziness, breathlessness, chest symptoms, confusion, persistent rapid heart rate, or bleeding should not be dismissed as routine recovery. Follow the discharge instructions and contact the surgical team.

A focused conversation should turn a low result into a coordinated plan.

Anemia before joint replacement is common enough to look for and important enough to understand. It is associated with higher transfusion and complication risks, but it is not an automatic reason to deny a needed hip or knee replacement. The best plan identifies the cause, treats what is correctable, allows enough time when possible, and weighs the anemia alongside the disability caused by arthritis.

Bring your laboratory history and medication list to an orthopedic consultation or call (808) 439-6201. Dr. Paul Morton can coordinate the joint-replacement plan with the clinicians managing anemia so the decision is specific, purposeful, and safe.

• Preoperative anemia and complications after total joint arthroplasty: systematic review and meta-analysis
• Preoperative anemia in total joint arthroplasty and periprosthetic joint infection
• Preoperative screening and intervention for mild anemia in elective hip and knee arthroplasty
• Preoperative iron treatment in anemic elective hip or knee arthroplasty patients
• 2023 AABB international red-blood-cell transfusion guidelines
• International consensus recommendations for anemia management in surgical patients