Hemoglobin

What Hemoglobin Measures

Each hemoglobin molecule is built from four protein subunits, and each subunit holds a heme group with an iron atom at its center. Oxygen binds reversibly to that iron, which is what lets red blood cells load oxygen in the lungs and release it in the tissues.^[1] The lab value itself is a concentration: how many grams of hemoglobin are present per deciliter of blood.^[7] So the test describes the blood's oxygen-carrying protein supply at the moment of the draw, not oxygen levels directly.

How It's Measured

Hemoglobin is measured from a standard venous blood draw, almost always as one line of a complete blood count.^[3] The CBC reads it alongside its neighbors: hematocrit, the red blood cell count, and indices like MCV that describe the size of those cells.^[2] Each value covers a different angle on the same red-cell picture, which is why labs report them together. Every result comes with the lab's own reference interval, and that interval can vary by lab and method.

Why People Track Hemoglobin

The body needs iron to build hemoglobin, and menstruation is a recurring, measurable form of blood loss. That connection shows up in population data: in a 2024 study of 473 premenopausal blood donors, menstrual blood loss independently predicted both hemoglobin and ferritin levels.^[4] For someone who already logs period flow, a hemoglobin result is one more number tied to a process their tracker records anyway. Ferritin covers the storage side of that same iron story, so the two values are often studied together.

How Go Go Gaia Tracks Hemoglobin

Go Go Gaia doesn't draw blood or run lab work. You can upload a hemoglobin result from a CBC you've already had done, and the app stores it as a dated data point in g/dL. From there it's charted on your timeline next to your logged period-flow data, so you can see where a draw fell relative to your cycle instead of reading the number in isolation.

What the Research Shows

Menstrual blood loss was an independent determinant of hemoglobin and ferritin levels in a cohort of 473 premenopausal blood donors, alongside factors like time since a person's last donation.^[4]

Hemoglobin also has a documented afterlife. When red blood cells reach the end of their lifespan, roughly 80% of the body's bilirubin is produced from the breakdown of their hemoglobin.^[5] A bilirubin value on a metabolic panel is, in large part, retired hemoglobin.

Glucose in the bloodstream attaches to hemoglobin as red blood cells circulate, and because those cells live about three months, the glycated fraction reflects average glucose over roughly that window. That fraction is reported as its own test, HbA1c.^[6]

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

Does Go Go Gaia measure hemoglobin?

No. Go Go Gaia doesn't draw blood or run labs. You get a hemoglobin result from a blood draw ordered through a clinician or lab service, then upload it to your Go Go Gaia account so it's stored and charted alongside your other tracked data.

How is hemoglobin different from ferritin?

Hemoglobin is the working protein that carries oxygen inside red blood cells, while ferritin is the protein that holds iron in storage inside cells. They sit at different points in the same iron story, which is why studies of iron status in people who menstruate often measure both together.

What does hemoglobin have to do with HbA1c?

HbA1c is hemoglobin that glucose has attached to. Because red blood cells live about three months, the share of hemoglobin carrying glucose reflects average blood glucose over roughly that window. It's the same protein measured from a different angle.