Total Hemoglobin (tHb), Mixed Sample

This test measures the total amount of hemoglobin in a blood sample that represents a mixture of venous blood returning from different parts of the body. Hemoglobin is the protein inside red blood cells that carries oxygen from your lungs to your tissues and helps carry carbon dioxide back to the lungs.

In many hospitals this measurement is performed on a blood gas or co-oximetry analyzer, often when clinicians need a rapid picture of oxygen delivery. Results may be reported as a concentration or, depending on the analyzer and method, as a fraction in specific contexts.

Your total hemoglobin level is a key marker of your blood’s capacity to carry oxygen. Clinicians use it to evaluate symptoms like fatigue, shortness of breath, chest discomfort, or dizziness, and to help assess blood loss, dehydration, or the need for transfusion. It is commonly checked in emergency and critical care settings, before and after surgery, and during treatment for conditions that affect red blood cells.

Immune and inflammatory conditions can influence hemoglobin. Autoimmune hemolytic anemia can lower levels by causing red blood cells to break down, while chronic inflammatory diseases can reduce red blood cell production. Tracking hemoglobin over time helps your care team understand disease activity, treatment response, and overall oxygen-carrying status.

Your result is interpreted alongside your symptoms, physical exam, and other blood tests, such as red cell indices and iron studies. A lower-than-expected value suggests anemia, which has many possible causes, including iron deficiency, chronic inflammation, blood loss, or hemolysis. A higher-than-expected value may reflect reduced plasma volume, living at high altitude, lung or heart disease with long-standing low oxygen, or a bone marrow condition.

One isolated result rarely tells the full story. If your number is outside the expected range, your clinician may repeat testing, review medications and hydration status, and order follow-up tests to look for nutritional deficiencies, hemolysis, inflammation, kidney disease, or other causes. Pregnancy, infancy, and recovery from illness can shift expected values, so your care team will interpret the result in that context.