An MCHC above 37 g/dL is considered abnormally high and warrants further evaluation. The normal range for adults is 32 to 36 g/dL, and values even slightly above that upper limit can signal an underlying condition affecting your red blood cells. MCHC doesn’t climb dramatically the way some lab values can, so even readings in the high 30s are taken seriously.
What MCHC Measures
MCHC stands for mean corpuscular hemoglobin concentration. It tells you how densely packed hemoglobin is inside each red blood cell. Hemoglobin is the protein that carries oxygen through your blood, so this number reflects how concentrated that oxygen-carrying molecule is within the cell itself. It’s one of several red blood cell indices included in a standard complete blood count (CBC).
Unlike many blood markers that can swing wildly, MCHC operates in a narrow band. The normal range of 32 to 36 g/dL doesn’t leave much room for variation. That’s because there’s a physical limit to how much hemoglobin a red blood cell can hold before it becomes rigid, fragile, or both. A result of 37 g/dL or higher is flagged as abnormal, and the higher it goes, the more likely it reflects a real problem rather than a lab quirk.
Why Truly High MCHC Is Uncommon
MCHC rarely rises far above the upper limit for a simple reason: red blood cells can only concentrate hemoglobin so much before they lose their normal flexibility. Healthy red blood cells are shaped like a disc with a slight indent in the center, which lets them squeeze through tiny blood vessels. When hemoglobin concentration gets too high inside the cell, it becomes stiff and spherical, and the body tends to destroy these abnormal cells quickly. This self-limiting process keeps MCHC from climbing to extreme levels in most situations.
Because of this, an MCHC reading above 37 g/dL always deserves investigation. Values in the range of 38 to 40 g/dL or higher are particularly concerning because they suggest either a genuine blood disorder or a laboratory error, both of which need to be sorted out.
Conditions That Cause Elevated MCHC
Hereditary Spherocytosis
This is one of the most classic causes of a genuinely elevated MCHC. It’s a genetic condition where the proteins that form the red blood cell’s outer membrane are defective. The membrane loses surface area while the hemoglobin inside stays the same, so the cell shrinks into a dense sphere rather than maintaining its normal flexible disc shape. These spherical cells are packed with hemoglobin relative to their size, which pushes MCHC upward. They’re also fragile and prone to being destroyed by the spleen, which can lead to anemia, jaundice, an enlarged spleen, and gallstones over time.
Autoimmune Hemolytic Anemia
In this condition, your immune system mistakenly produces antibodies that attack your own red blood cells. As cells are destroyed, hemoglobin gets released and the remaining cells may show higher-than-normal concentration. Symptoms include fatigue, pale skin, weakness, yellowing of the skin and eyes (jaundice), chest pain, fever, and abdominal discomfort from an enlarged spleen. The elevated MCHC here is a marker of the ongoing destruction rather than the primary problem.
Severe Burns
People hospitalized with significant burns often develop a form of hemolytic anemia, where heat damage to red blood cells causes them to break apart. This destruction can temporarily push MCHC readings higher.
When the Number Is Wrong: False Elevations
A surprisingly common explanation for a high MCHC result is laboratory interference, meaning something in your blood sample caused the analyzer to produce an inaccurate reading. This is important to understand because it can save you unnecessary worry.
Several factors can falsely inflate MCHC:
- High blood lipids (lipemia): If your blood has elevated fat content, perhaps because you ate before the test, it interferes with the hemoglobin measurement and produces a falsely high MCHC.
- High bilirubin levels: Very elevated bilirubin, the yellowish compound produced when red blood cells break down, can cause similar interference with hemoglobin readings.
- Cold agglutinins: Certain antibodies, often associated with infections like mycoplasma pneumonia, cause red blood cells to clump together at cooler temperatures. This clumping throws off the cell count and artificially raises MCHC. Warming the sample and rerunning the test usually corrects the problem.
- Abnormal proteins in the blood: Conditions involving excess antibody production can create turbidity in the sample, again pushing hemoglobin readings falsely high.
If your MCHC comes back elevated but you feel fine and have no symptoms, there’s a reasonable chance the result is a lab artifact. Repeating the test, sometimes with special sample handling, often clears things up.
Symptoms to Watch For
A high MCHC number on its own doesn’t produce symptoms. What you feel depends on the condition driving the elevation. The most common signs overlap with anemia and red blood cell destruction:
- Fatigue and weakness that doesn’t improve with rest
- Pale or yellowish skin, particularly yellowing of the whites of your eyes
- Dark urine, which can signal red blood cell breakdown
- Abdominal fullness or pain on the left side, from an enlarged spleen
- Shortness of breath during activities that didn’t used to wind you
If your blood work shows an elevated MCHC and you’re experiencing several of these symptoms, the combination points toward active hemolysis, meaning your red blood cells are being destroyed faster than your body can replace them.
How High MCHC Is Evaluated
An elevated MCHC is never treated directly. It’s a clue, not a diagnosis. The next step is figuring out why it’s elevated. That typically means looking at the rest of your CBC results, particularly your red blood cell count, hemoglobin, hematocrit, and the shape of your red blood cells on a blood smear. A blood smear lets a technician look at your cells under a microscope to spot spherocytes (the round, dense cells seen in hereditary spherocytosis) or signs of cell destruction.
If hereditary spherocytosis is suspected, additional testing evaluates how fragile your red blood cells are when placed in solutions of varying concentration. For autoimmune hemolytic anemia, a test called a direct antiglobulin (Coombs) test checks whether antibodies are attached to your red blood cells. Treatment depends entirely on the underlying cause. Some people with mild hereditary spherocytosis need nothing more than folic acid supplements and monitoring, while severe cases may eventually require removal of the spleen. Autoimmune hemolytic anemia is typically managed by suppressing the immune response that’s attacking the red blood cells.
Putting the Numbers in Context
If you’re looking at your lab results and see an MCHC of 36.5 or 37 g/dL, that’s borderline and may not mean anything clinically significant, especially if the rest of your blood count looks normal. The further above 37 the value climbs, the more likely it is to reflect either a true blood cell abnormality or a sample issue that needs to be addressed.
MCHC is most useful when interpreted alongside your other red blood cell indices, not in isolation. A high MCHC paired with a low red blood cell count and visible spherocytes on a smear tells a very different story than a high MCHC with everything else in range. The number matters, but the pattern matters more.