What Does a High MCHC on a Blood Test Mean?

A high MCHC means the report suggests haemoglobin is more concentrated inside your red blood cells than the laboratory expects. MCHC (mean corpuscular haemoglobin concentration) is a calculated red cell index in a full blood count, also called a complete blood count. A genuinely high value is uncommon, so the first question is often whether the sample itself caused a false reading.

MedlinePlus lists hereditary spherocytosis and haemolytic anaemia, where red cells are destroyed faster than they are replaced, as possible causes of a high MCHC. Laboratory reviews also describe several sample and measurement problems that can push the number up. This guide helps you understand those possibilities and prepare questions. It cannot tell you which one applies to you.

Do not wait for a routine repeat test if you notice new yellowing of the skin or the whites of the eyes. The NHS advises asking for an urgent GP appointment or getting help from NHS 111 for jaundice; elsewhere, use your local urgent care service. A clinical review describes sudden jaundice, or blood in the urine, alongside anaemia as signs that should prompt doctors to consider haemolysis.

Get help sooner if any of the following happen. For chest pain, severe breathlessness or fainting, call your local emergency number.

• Yellow skin or eyes, especially with dark urine or new tiredness.
• Red, brown or cola-coloured urine.
• Breathlessness, a racing heartbeat or dizziness that is new or getting worse.
• Pain or a full feeling in the upper left side of the abdomen, or pain in the upper abdomen with nausea.
• Marked paleness or exhaustion in a child with a known or suspected red cell condition.

MedlinePlus gives a typical adult range of 32 to 36 g/dL, which is the same as 320 to 360 g/L. It notes that normal ranges vary slightly between laboratories. Use the range printed beside your own result, and check the units, because some laboratories report in g/dL and others in g/L.

MCHC is worked out from the haemoglobin measurement together with the red cell count or haematocrit. That means an error in any of those measurements carries straight into MCHC. It is one reason laboratories treat an unexpectedly high MCHC as something to check.

Yes. A 2022 laboratory review and a 2025 review by a French-speaking haematology laboratory group both describe a falsely high MCHC as a well-known sign of sample interference. Some laboratories use a high MCHC as a built-in check before releasing results. They may warm the sample, adjust it and run it again, add a comment, or hold back the affected indices.

The reviews list these common causes of a falsely high reading:

• Cold agglutinins: antibodies that make red cells clump together as the sample cools. The analyser counts clumps as single cells, so the red cell count drops and MCHC rises. Warming the sample to body temperature and running it again usually helps.
• Lipaemia: very fatty plasma, for example from very high triglycerides or a lipid infusion, can make haemoglobin read falsely high.
• Very high bilirubin: strong jaundice in the plasma can interfere with the haemoglobin reading.
• Haemolysis in the tube: red cells damaged during a difficult blood draw or rough handling release haemoglobin into the sample.
• Underfilled tubes and some abnormal blood proteins, which can also distort the indices.

Hereditary spherocytosis is an inherited condition in which red cells are round rather than disc-shaped. These cells break down faster than normal, mainly in the spleen. Cleveland Clinic describes possible signs such as tiredness, pale skin, jaundice, an enlarged spleen and gallstones. It is often diagnosed in childhood, but Cleveland Clinic notes that some people have no signs until their 30s or 40s.

A raised MCHC is one of the clues doctors look for, alongside round cells (spherocytes) on a blood film and signs of red cell breakdown. Cleveland Clinic notes that clinicians ask about family history because the condition often runs in families. A high MCHC on its own does not confirm the diagnosis.

Haemolysis means red cells are destroyed faster than the bone marrow replaces them. The American Family Physician review explains that spherocytes can appear in immune-related haemolysis as well as inherited conditions, so the pattern needs interpreting as a whole. Cold agglutinin disease is one immune cause, and it can both damage red cells in the body and interfere with the blood count in the tube.

If haemolysis is a question, clinicians may look at tests such as:

• A blood film, where a specialist looks at red cell shape under a microscope.
• Reticulocytes (young red cells), which usually rise when the marrow is replacing lost cells.
• Bilirubin, lactate dehydrogenase (LDH) and haptoglobin, which can change when red cells break down.
• A direct antiglobulin (Coombs) test, which helps separate immune causes from non-immune ones.

Take the full report, including MCHC, haemoglobin, MCV, MCH, red cell count, units and the laboratory's reference range. Bring earlier results if you have them. These questions can help:

• Was my MCHC flagged or commented on by the laboratory, and was the sample checked or rerun?
• Could cold agglutinins, fatty plasma, jaundice or a damaged sample explain this result?
• Is my haemoglobin normal or low, and do the other red cell indices fit together?
• Should the test be repeated, and do I need to do anything differently before the next sample?
• Is a blood film or any test for red cell breakdown needed?
• Does my family history of anaemia, jaundice, gallstones or spleen removal matter here?
• Which symptoms should make me seek help before the next planned review?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with an unexpected high MCHC had their result checked, repeated or followed up can help you notice questions you had not thought to ask, such as whether the sample was rerun.

Similar cases are a way to prepare, not an answer. They cannot tell you the cause of your result, and every person's blood count, history and symptoms differ. Take your questions to the clinician who can see your full results.