High MCHC on Your Blood Test
Why a high MCHC is more often a laboratory quirk than a diagnosis, the genuine causes when it is not, and the tests your GP should run next — in plain English.
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The Quick Answer
MCHC stands for mean corpuscular haemoglobin concentration — the average concentration of haemoglobin packed inside each of your red blood cells. Australian labs report a normal range of roughly 320-360 g/L (equivalently 32-36 g/dL).
Here is the headline that makes this page worth reading: a high MCHC is the one full blood count result that is more often a laboratory artefact than a genuine disease. Red cells are already close to physically saturated with haemoglobin at a normal MCHC — there is very little biological room for a real result to climb much higher. When an analyser reports MCHC above about 370 g/L, laboratory scientists treat it as a flag to check the sample, not as a patient diagnosis.
What Is MCHC and Why Is a High Result Unusual?
MCHC is not measured directly — it is calculated by the laboratory analyser as your haemoglobin divided by your haematocrit. It describes how densely each red blood cell is packed with haemoglobin, which is a different question to how many red cells you have (haemoglobin), how big each one is (MCV), or how much haemoglobin sits inside each cell in absolute terms (MCH).
A normal red blood cell is already carrying close to the maximum amount of haemoglobin its structure can hold without becoming rigid and fragile. That physical ceiling is exactly why a truly elevated MCHC is uncommon — there is only so much haemoglobin a healthy, flexible red cell can contain before something has to give.
In practice, most high readings come from something interfering with the measurement itself — broken cells spilling haemoglobin into the surrounding plasma, a fatty sample scattering the light the analyser uses, or antibodies clumping cells together in a cold tube. Genuine causes exist, but they are the exception, and they almost always involve red cells that are structurally abnormal rather than a temporary lab hiccup.
Causes of High MCHC
Causes are grouped as artefactual (the reading is false, caused by the sample or the analyser) or genuine (the reading reflects a real change in your red cells). Artefactual causes are listed first because they explain the large majority of high MCHC results seen in everyday practice.
In-vitro haemolysis
Red cells break apart during a difficult blood draw or rough transport, spilling haemoglobin into the plasma. The analyser still measures that haemoglobin, but the cells no longer contribute volume, so MCHC is falsely raised. Labs often flag this as a haemolysed sample.
Lipaemia
A fatty, milky-looking sample — usually from a non-fasting high-fat meal or very high triglycerides — interferes with the optical haemoglobin measurement, pushing MCHC artificially high. A repeat fasting sample usually resolves it.
Cold agglutinins
Antibodies that clump red cells together when a sample cools below body temperature. The analyser counts each clump as one giant cell, which drops the measured haematocrit and pushes MCHC up. Classically fixed by re-running the sample warmed to 37 degrees.
Very high white cell or platelet count
Extreme leukocytosis or a very high platelet count can add turbidity that confuses the optical haemoglobin reading, nudging MCHC above the reference range without any real change in the red cells themselves.
Old or underfilled sample
A blood tube left too long before testing, or an EDTA tube not filled to the correct level, changes cell shape and volume and can distort the calculated MCHC. Good collection technique prevents most of this.
Hereditary spherocytosis
An inherited red cell membrane defect makes cells small, round and dense rather than the normal flexible disc shape. Look for a family history of anaemia, gallstones at a young age, jaundice, or a previous splenectomy.
Autoimmune haemolytic anaemia
Antibody-coated red cells lose fragments of membrane as they pass through the spleen, becoming spherocyte-like and pushing MCHC upward. Confirmed with a positive direct antiglobulin (Coombs) test.
Severe burns
Heat damage to circulating red cell membranes can genuinely raise MCHC in the days after a significant burn injury, alongside other markers of cell damage.
Sickle cell disease (especially HbSC)
Haemoglobin SC disease in particular is associated with dense, dehydrated red cells and a genuinely raised MCHC. More common in people of African, Mediterranean, Middle Eastern or South Asian background.
Xerocytosis (hereditary cellular dehydration)
A rare inherited membrane disorder in which red cells lose potassium and water, becoming abnormally dense. Usually identified only after more common causes have been excluded.
Symptoms That Can Accompany a High MCHC
Most people with a high MCHC feel completely well, because most high MCHC results do not reflect anything happening in the body at all. Symptoms tend to appear only when a genuine cause is also driving active haemolysis — red cells being destroyed faster than the bone marrow can replace them.
No symptoms at all
By far the most common scenario. A high MCHC picked up on a routine test, with no anaemia and no other abnormal results, usually reflects the sample rather than your body and needs no action beyond a repeat test.
Fatigue and weakness
Appears when a genuine cause is also driving anaemia. The tiredness is caused by reduced oxygen delivery as red cells are destroyed faster than they are made.
Jaundice (yellow skin or eyes)
A sign that red cells are being broken down faster than usual, releasing bilirubin. Suggests active haemolysis and should prompt a prompt review by your GP.
Dark urine
Haemoglobin or its breakdown products spilling into the urine is a marker of significant haemolysis, not simply dehydration. Worth mentioning to your GP even if you otherwise feel well.
Gallstones or right-upper-abdominal pain
Chronic mild haemolysis, as seen in hereditary spherocytosis, produces pigment gallstones that can appear well before middle age.
An enlarged spleen
The spleen works overtime removing abnormal red cells in conditions such as spherocytosis or autoimmune haemolytic anaemia, and can become enlarged and tender under the left ribs.
Pale skin, lips or nail beds
A general sign of anaemia when red cell destruction outpaces production, best assessed in good natural light against the inside of the lower eyelid.
Fingers or toes turning white or blue in the cold
A red-flag combination alongside high MCHC that points towards cold agglutinin disease, where antibodies clump red cells in cooler parts of the body.
Red Flags — When to See Your GP Promptly
Most people with a high MCHC can simply wait for a routine repeat test. But some combinations of findings are worth a phone call to your GP within a week or two rather than waiting for the next scheduled check-up:
High MCHC plus anaemia and a raised reticulocyte count
This combination suggests active haemolysis — red cells being destroyed faster than the bone marrow can replace them — and is the pattern that most often needs real investigation rather than a simple repeat test.
Jaundice or yellowing of the eyes
A visible sign that bilirubin is building up from red cell breakdown. Worth a same-week GP appointment, sooner if you also feel unwell or have abdominal pain.
Dark urine
Suggests haemoglobin is being released into the bloodstream faster than the body can clear it — a marker of clinically significant haemolysis.
Gallstones diagnosed before age 40
Pigment gallstones at a young age are a classic downstream sign of chronic haemolysis, most often from undiagnosed hereditary spherocytosis.
An enlarged spleen on examination
Suggests the spleen is working hard removing abnormal red cells, seen in both hereditary spherocytosis and autoimmune haemolytic anaemia.
Family history of anaemia, jaundice, gallstones or splenectomy
Hereditary spherocytosis runs in families and is often under-recognised for a generation or two before someone is formally tested.
Fingers or toes turning white or blue in the cold, alongside a high MCHC
Points towards cold agglutinin disease, where cold-sensitive antibodies clump red cells and interfere with the blood count as well as circulation.
What Your GP Will Do Next — The Workup
Australian GPs follow a fairly predictable pathway when a high MCHC does not resolve on its own. Knowing the sequence helps you understand why each test is being ordered and what a normal or abnormal result at each step actually rules in or out.
Repeat the FBC on a fresh sample
The single most useful step. Because a genuinely high MCHC is biologically hard to produce, many results simply disappear when the test is repeated with careful, prompt sample handling.
Check the laboratory quality comments
Pathology labs routinely flag samples as haemolysed, lipaemic, or affected by cold agglutinins. These comments, often overlooked by patients, frequently explain the whole result on their own.
Order a blood film
A laboratory scientist examines your red cells under a microscope, looking specifically for spherocytes — small, dense, round cells without the usual central pallor — the hallmark of hereditary spherocytosis and autoimmune haemolytic anaemia.
Check the reticulocyte count
A raised reticulocyte count means the bone marrow is working overtime to replace red cells, a strong sign that genuine haemolysis, not a lab artefact, is behind the result.
Run a haemolysis screen
Bilirubin, LDH and haptoglobin together confirm or exclude active red cell breakdown. Raised bilirubin and LDH with a low haptoglobin is the classic haemolysis pattern.
Direct antiglobulin test (Coombs test)
Detects antibodies coating the red cell surface, separating autoimmune haemolytic anaemia (test positive) from hereditary spherocytosis (test negative).
EMA binding test or osmotic fragility test
These specialised tests confirm hereditary spherocytosis by measuring how fragile the red cell membrane is, and are usually arranged through a haematology laboratory.
Fasting lipid panel, and haematologist referral if confirmed
A fasting lipid panel checks whether high triglycerides explain a lipaemic sample. If haemolysis is confirmed by the steps above, referral to a haematologist guides ongoing management.
Treatment — What Happens Once You Know the Cause
Most of the time: nothing, beyond a repeat test
If the sample was haemolysed, lipaemic, or affected by cold agglutinins, no treatment is needed at all — the fix is a fresh, properly handled sample. This outcome covers the large majority of high MCHC results your GP will see.
Hereditary spherocytosis
Mild cases often need only folic acid supplementation to support ongoing red cell production and regular monitoring for gallstones. More severe cases, especially with significant anaemia, may be referred for splenectomy, which removes the organ destroying the abnormal cells. Vaccination against pneumococcus, meningococcus and Haemophilus influenzae type b is required before splenectomy, because a spleen-free patient has a lifelong higher risk of severe infection.
Autoimmune haemolytic anaemia
First-line treatment is usually a course of corticosteroids to dampen the antibody response, with other immunosuppressant medications used if steroids alone are not enough. Your haematologist will also look for an underlying trigger, such as a lymphoproliferative disorder, autoimmune disease or certain medications.
Cold agglutinin disease
Simple measures such as keeping hands, feet and the whole body warm can reduce symptoms day to day. If an underlying condition is found, treating it — and in more severe or persistent cases, targeted medication such as rituximab — brings the haemolysis under control.
Lipaemia and other pre-analytical causes
A repeat fasting sample usually clears a lipaemic result. If a fasting lipid panel shows genuinely high triglycerides, your GP will address that separately through diet, lifestyle changes or medication, which also protects your cardiovascular health.
How MCHC Differs From MCH and MCV
These three red cell indices are reported together and are routinely confused because they all describe red blood cells, but each answers a different question.
MCV
Mean Corpuscular VolumeThe size (volume) of the average red blood cell
Unit: fL (femtolitres)Formula: Haematocrit ÷ red cell countMCH
Mean Corpuscular HaemoglobinThe amount (mass) of haemoglobin inside the average red blood cell
Unit: pg (picograms)Formula: Haemoglobin ÷ red cell countMCHC
Mean Corpuscular Haemoglobin ConcentrationThe concentration of haemoglobin packed inside each red blood cell
Unit: g/L (or g/dL)Formula: Haemoglobin ÷ haematocritIn short: MCV asks how big each cell is, MCH asks how much haemoglobin sits inside each cell, and MCHC asks how tightly that haemoglobin is packed once cell size is accounted for. A high MCV without a high MCHC (see our high MCV guide) usually points to B12 or folate deficiency, while a high MCHC with a normal or low MCV points much more specifically towards spherocytosis or a sample artefact. If your report also shows a raised MCH, our high MCH guide explains how that measurement fits into the picture.
High MCHC — Frequently Asked Questions
What does it mean if my MCHC is high?
A high MCHC means the haemoglobin inside your red blood cells is more concentrated than the Australian reference range of roughly 320-360 g/L (32-36 g/dL). Unlike most abnormal blood results, a high MCHC is more often caused by how the sample was collected or handled than by a genuine disease process — in-vitro haemolysis, a fatty (lipaemic) sample, or cold-sensitive antibodies clumping red cells can all falsely raise the reading. Genuine causes exist too, most often hereditary spherocytosis, but your GP will usually start by simply repeating the test on a fresh sample.
What is the normal range for MCHC in Australia?
Australian pathology labs typically report a normal MCHC range of about 320-360 g/L, sometimes written as 32-36 g/dL — the two units describe exactly the same concentration. Results between 360 and 370 g/L are usually considered borderline and rarely mean anything on their own. Most labs treat any result above about 370 g/L as a trigger to check the sample itself for problems such as haemolysis, lipaemia or cold agglutinins before assuming the number reflects something happening inside your body.
Is a high MCHC always something to worry about?
No. A high MCHC is the one full blood count abnormality that is more often a laboratory artefact than a genuine finding, because red blood cells are already close to fully saturated with haemoglobin at a normal MCHC — there is very little room for a real result to climb much higher. Most high readings disappear once the test is simply repeated on a fresh, well-handled sample. Genuine causes are uncommon and are usually picked up because the high MCHC appears alongside other clues, such as anaemia, jaundice or a family history of similar blood problems.
What is hereditary spherocytosis?
Hereditary spherocytosis is an inherited fault in the red blood cell membrane that makes cells small, round and rigid — called spherocytes — instead of their normal flexible disc shape. These cells are removed from the circulation faster than usual, especially by the spleen, causing ongoing mild-to-moderate haemolysis. It is the classic genuine cause of a persistently raised MCHC, typically in the range of 360-380 g/L. Clues include a family history of anaemia, jaundice, gallstones at a young age, or a previous splenectomy. A blood film and an EMA binding test confirm the diagnosis.
Can dehydration cause a high MCHC?
General body dehydration does not meaningfully raise MCHC, because MCHC measures the haemoglobin concentration inside each individual red cell, not the concentration of your blood as a whole — that effect shows up in haematocrit and total protein instead. A separate, much rarer process called cellular dehydration, or xerocytosis, can raise MCHC because the red cells themselves lose water and become abnormally dense, but this is an inherited condition rather than something caused by not drinking enough water. If your GP mentions dehydration alongside MCHC, they are more likely explaining an unusual-looking sample, not diagnosing you.
What tests come after a high MCHC?
Your GP will almost always repeat the full blood count first, since many high MCHC results are laboratory artefacts that vanish on a fresh sample. If it persists, expect a blood film to look for spherocytes, a reticulocyte count, and a haemolysis screen covering bilirubin, LDH and haptoglobin. A direct antiglobulin test, also called a Coombs test, helps distinguish autoimmune haemolytic anaemia from hereditary spherocytosis, and an EMA binding test or osmotic fragility test can confirm spherocytosis specifically. A fasting lipid panel may be added if the original sample looked lipaemic.
Can high MCHC be caused by a lab error?
Yes, and this is by far the most common explanation. In-vitro haemolysis from a difficult blood draw, a fatty (lipaemic) sample after a high-fat meal, cold agglutinin antibodies clumping red cells in a cooling sample, or a very high white cell or platelet count can all interfere with the analyser and falsely raise the reported MCHC. Laboratory scientists are trained to spot these patterns and will often flag the result as haemolysed or lipaemic, or repeat the count, before it reaches your GP. Simply repeating the blood test on a fresh, properly handled sample resolves most of these cases.
Related Reading
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This page provides general educational information about a raised MCHC. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your GP about abnormal blood test results — they have access to your full medical history and can interpret your results in context. SmarterBlood does not provide medical care.