A high MCHC means your red blood cells are carrying more hemoglobin than normal relative to their size. MCHC stands for mean corpuscular hemoglobin concentration, and the normal range is 32 to 36 g/dL. A result above 36 g/dL is considered elevated, though in some cases a high reading is simply a lab error rather than a sign of disease.
MCHC is one of several values included in a complete blood count (CBC), the routine blood test your doctor orders during checkups or when investigating symptoms like fatigue. On its own, a high MCHC doesn’t tell you what’s wrong. It points your doctor toward a specific set of conditions that need further investigation.
How MCHC Gets Too High
There are two basic ways MCHC rises above normal. The first is when hemoglobin becomes more concentrated inside each red blood cell. This happens when cells lose water (dehydration at the cellular level) or lose part of their outer membrane, shrinking the cell while the hemoglobin stays put. The result is a smaller, denser cell packed with more hemoglobin per unit of volume.
The second mechanism involves red blood cells breaking apart, a process called hemolysis. When fragile red blood cells rupture, they release hemoglobin into the surrounding plasma. Automated blood analyzers can pick up this free-floating hemoglobin and factor it into the MCHC calculation, pushing the number higher than it should be.
Common Causes of High MCHC
Hereditary Spherocytosis
This is one of the most characteristic causes of a genuinely elevated MCHC. In hereditary spherocytosis, red blood cells lose their normal disc shape and become round (spherical). The cells lose membrane surface area and become mildly dehydrated, which concentrates the hemoglobin inside them. MCHC values above 35 to 36% are common in people with this condition. On a blood smear, these spherocytes look darker than normal cells and lack the pale center you’d normally see.
Autoimmune Hemolytic Anemia
In this condition, your immune system mistakenly attacks your own red blood cells, causing them to break apart prematurely. The destruction releases hemoglobin and produces small, dense cell fragments that raise MCHC. This can develop on its own or alongside other autoimmune conditions like lupus.
Severe Burns
Extensive burns damage red blood cells directly, causing widespread hemolysis. The combination of cell destruction and fluid shifts can produce a high MCHC reading in the acute period after a burn injury.
Liver Disease and Thyroid Problems
Liver disease can affect how red blood cells are produced and how long they survive, sometimes leading to elevated MCHC. An overactive thyroid gland can also raise MCHC, likely through its broad effects on metabolism and blood cell turnover.
When the Lab Result Is Wrong
A surprisingly common reason for high MCHC is a lab artifact, meaning nothing is actually wrong with your blood. Several things can interfere with the automated analyzer and produce a falsely elevated reading.
Cold agglutinins are the most well-known culprit. These are antibodies that cause red blood cells to clump together at cool temperatures. When a blood sample cools slightly during transport or handling, the clumping tricks the machine into measuring fewer, larger red blood cells than are actually present. This artificially inflates the MCHC. Some analyzers will flag readings above 36 or 37.5 g/dL as potentially spurious for this reason.
Lipemia (high fat content in the blood, often from a recent meal) and icterus (high bilirubin, which causes jaundice) both create turbidity in the blood sample. This cloudiness interferes with the light-based measurement of hemoglobin, pushing the value up. A very high white blood cell count or the presence of abnormal proteins in the blood can cause similar interference. If your MCHC comes back high and your doctor suspects a lab error, they may simply repeat the test with a fresh sample, sometimes warming it first to resolve cold agglutinin clumping.
Symptoms to Watch For
A high MCHC number itself doesn’t cause symptoms. What you feel depends entirely on the underlying condition driving it.
If hemolytic anemia is the cause, you may notice fatigue, weakness, pale skin, a yellowish tint to the eyes or skin (jaundice), a rapid heartbeat, or discomfort in the upper left abdomen where the spleen sits. The spleen often enlarges because it’s working overtime to clear damaged red blood cells.
If the elevated MCHC is linked to an overactive thyroid, symptoms tend to look different: unexplained weight loss, excessive sweating, increased hunger, restlessness, and heart palpitations. Liver-related causes may bring nausea, vomiting, and pain in the upper right abdomen.
Some people with a mildly elevated MCHC feel perfectly fine, especially if the elevation is small or caused by a lab artifact. The absence of symptoms doesn’t automatically mean there’s no underlying issue, but it does change the urgency of follow-up.
What Happens After a High Result
When your MCHC comes back elevated, your doctor will look at it alongside other values on the CBC, particularly the MCV (average cell size), red blood cell count, and hemoglobin level. A high MCHC with a low MCV, for example, points strongly toward spherocytosis or another condition involving small, dense red blood cells.
The next step is often a peripheral blood smear, where a lab technician examines your blood under a microscope. They’re looking for telltale cell shapes: spherocytes (round, dark cells without a pale center), clumped red blood cells suggesting cold agglutinins, or fragments of destroyed cells. This single test can narrow the diagnosis significantly.
Depending on what the smear shows and your symptoms, further testing might include a reticulocyte count (which measures how fast your body is making new red blood cells), a direct antiglobulin test to check for autoimmune hemolysis, thyroid function tests, or liver panels.
How Underlying Conditions Are Treated
Treatment targets whatever is causing the high MCHC, not the lab value itself.
For hereditary spherocytosis, mild cases may need nothing more than monitoring and folic acid supplementation to support red blood cell production. More severe cases, where ongoing red blood cell destruction causes significant anemia or an enlarged spleen, may eventually require surgical removal of the spleen. This doesn’t fix the cell shape, but it removes the organ responsible for filtering out and destroying the abnormal cells.
Autoimmune hemolytic anemia is typically managed with medications that suppress the immune system’s attack on red blood cells. If the anemia is severe, blood transfusions may be needed in the short term.
When the cause is thyroid disease or liver disease, treating that condition usually brings the MCHC back toward normal as a secondary effect. And when a lab artifact is to blame, no treatment is needed at all. Your doctor may simply note it in your chart and recheck with a properly handled sample to confirm your values are actually normal.