17683 Hematocrit

Overview

Hematocrit is a blood test result. It tells you what share of your blood, by volume, is made up of red blood cells. Red blood cells carry oxygen from your lungs to the rest of your body. Doctors often write hematocrit as a percentage. For example, a hematocrit of 45% means that 45% of your blood volume is red blood cells and the rest is mostly plasma, the watery part of blood. Hematocrit is usually measured as part of a full blood count (also called a complete blood count, or CBC). A hematocrit that is too low or too high is not a diagnosis on its own. It is a clue that helps your doctor work out what is going on.

Very common. Hematocrit is one of the most frequently ordered blood tests, and abnormal results are everyday findings in general practice. Low hematocrit from iron deficiency is especially common, particularly in people who have heavy periods. Many abnormal results turn out to have a simple explanation and are not a sign of anything serious.

Hematocrit can be checked at any age, from babies to older adults. Low results are more common in people who menstruate, pregnant women, vegetarians and vegans who do not get enough iron or vitamin B12, people with long-term illnesses, and people who have had recent bleeding. Higher results are more common in smokers, people living at high altitude, people who are dehydrated, and people with sleep apnea or long-term lung problems.

Symptoms

Common symptoms

• Feeling very tired or weak, even after rest
• Looking pale, especially around the face, lips and inside the eyelids
• Shortness of breath with everyday activity such as climbing stairs
• Dizziness or light-headedness when standing up
• Cold hands and feet
• A fast or pounding heartbeat
• Headaches or trouble concentrating
• For high hematocrit: flushing, headache, blurred vision, unusual tiredness, or itchy skin after a warm shower

Symptoms in children

• Looking pale or unusually washed out
• Being more sleepy or less playful than usual
• Poor appetite or slow weight gain
• Getting out of breath quickly during play
• Frequent infections or slow recovery from illness
• In babies, feeding less well or being hard to wake for feeds

Symptoms in older adults

• Tiredness that is put down to 'just getting older'
• Breathlessness on mild exertion, such as walking to the shops
• Palpitations or an irregular heartbeat
• Confusion, poor concentration or unsteadiness that is new
• Chest discomfort, especially with activity
• Symptoms that flare up alongside other long-term conditions such as kidney or heart disease

Causes

Main causes

• Low hematocrit: losing blood, for example from heavy periods or slow bleeding in the gut
• Low hematocrit: not having enough iron, vitamin B12 or folate (these are needed to make red blood cells)
• Low hematocrit: long-term kidney disease, because the kidneys make a hormone that tells the body to produce red blood cells
• Low hematocrit: long-term inflammation or infection, which can slow red blood cell production
• Low hematocrit: pregnancy, because the blood volume increases and the red cells become more diluted
• Low hematocrit: problems with the bone marrow, where blood cells are made, or side effects of some medical treatments
• High hematocrit: not drinking enough fluids (dehydration), which makes the blood more concentrated
• High hematocrit: smoking, sleep apnea (breathing pauses during sleep) or long-term lung disease, because the body makes more red cells to cope with low oxygen
• High hematocrit: living at high altitude, where there is less oxygen in the air
• High hematocrit: some hormone treatments, and rarely a blood condition called polycythemia vera (a disorder where the body makes too many red cells)

Risk factors

• Heavy or long-lasting periods
• Pregnancy
• A diet low in iron, vitamin B12 or folate
• Vegetarian or vegan diets without suitable supplements or fortified foods
• Long-term conditions such as kidney disease, inflammatory bowel disease, or rheumatoid arthritis
• Stomach ulcers or taking medicines that can irritate the stomach lining
• Family history of blood disorders
• Smoking
• Living at high altitude
• Being overweight, which raises the risk of sleep apnea
• Recent surgery, major injury or blood loss

When to see a doctor

See a doctor urgently if:

• You have chest pain or severe breathlessness — call your local emergency number straight away
• You faint, have a seizure, or notice sudden weakness or speech changes
• You are bleeding heavily or passing black stools
• Your heartbeat feels very fast or irregular and you feel unwell
• A child looks pale, is very sleepy, or is not feeding or drinking

Book a routine appointment if:

• You feel more tired than usual for more than a few weeks
• You have noticed unusual pallor, breathlessness or a pounding heart
• A blood test has shown a low or high hematocrit and you have not yet discussed it with a doctor
• You have heavy periods or a change in your bowel habits
• You have a long-term condition and want to check your blood levels

Diagnosis

Hematocrit is found from a small blood sample, usually taken from a vein in your arm. The sample goes to a laboratory, where it is analysed by machine. Your doctor will interpret the number alongside your other blood results, your symptoms, your medical history and any medicines you take. If the result is unusual, they may repeat the test or arrange further checks to find the cause.

Tests that may be done

• Full blood count (complete blood count), which includes hematocrit, hemoglobin and red cell size
• A repeat blood test, to check whether a first result was a one-off
• Iron studies, to look for iron deficiency
• Vitamin B12 and folate levels
• Kidney and liver function tests
• Reticulocyte count, which shows whether your bone marrow is making new red cells
• A blood film (a look at your blood cells under a microscope)
• Tests for long-term inflammation or infection
• In some cases, a sleep study, oxygen level checks, or referral to a blood specialist

What to expect at your appointment

Having blood taken takes a few minutes and feels like a quick sting. You may get a small bruise afterwards. Most results come back within a few days, though some tests take longer. Your doctor's surgery or clinic will tell you how and when to get your results. Bring a list of your medicines and mention any supplements you take, as some can affect blood results.

Treatment

Treatment depends entirely on why your hematocrit is abnormal. Hematocrit itself is not usually treated directly — instead, your doctor looks for and treats the underlying cause. If your result is only slightly outside the normal range and you feel well, you may not need any treatment at all, just a repeat check in a few months. Always talk to your doctor before starting supplements or making big changes, because some vitamins and minerals can be harmful in large amounts.

Self-care at home

• Drink enough water through the day, especially in hot weather or during exercise
• Eat iron-rich foods such as beans, lentils, leafy greens, eggs, and lean meat if you eat it
• Include foods with vitamin C alongside plant sources of iron, as this helps your body absorb it
• Include sources of vitamin B12 and folate, such as fortified foods, dairy, eggs, and leafy greens
• Cut down or stop smoking, and avoid second-hand smoke
• Keep up gentle regular activity, but rest when you feel tired
• Keep a simple note of your symptoms so you can describe them clearly at appointments
• Tell your doctor or pharmacist about all supplements and medicines you take

Medical treatments

Your doctor will focus on the cause. For low hematocrit, this may mean treating a source of bleeding, advising on diet, or recommending supplements if you are deficient in a vitamin or mineral. For long-term conditions such as kidney disease, the underlying condition is managed, and in some cases hormone-based treatments that support red blood cell production may be considered by a specialist. For high hematocrit, treatment may include treating dehydration, managing sleep apnea or lung disease, stopping smoking, or — if a blood condition is found — specialist care such as removing some blood (venesection) or other treatments prescribed by a hematologist. You should never start or stop any treatment without speaking to your healthcare team.

When is surgery considered?

Surgery is not used to treat hematocrit itself. Occasionally, a procedure may be needed to deal with the underlying cause — for example, treating a bleeding ulcer or removing a polyp that is causing slow blood loss. If a rare blood or bone marrow condition is found, a specialist team will explain whether any procedure is appropriate for you.

Living with this condition

Most people with an abnormal hematocrit carry on with normal life once the cause is understood and managed. If you feel tired, plan your day with short rests rather than pushing through. If you have a high hematocrit, keeping well hydrated matters more than usual. Keep your appointments for repeat blood tests, and tell your doctor if your symptoms change.

Lifestyle tips

• Stay hydrated, particularly before and after exercise
• Eat a balanced diet with enough iron, vitamin B12 and folate
• Avoid smoking and limit alcohol
• Get regular, moderate exercise that suits your energy levels
• Aim for consistent, good-quality sleep, and ask about sleep apnea if you snore heavily or feel unrefreshed
• Manage stress with simple techniques such as walking, breathing exercises or talking to someone

Diet and exercise

Food is one of the most useful things you can influence. Iron from meat, poultry and fish is absorbed more easily than iron from plants, but plant sources such as lentils, beans, tofu, spinach and fortified cereals are still valuable — pairing them with vitamin C (for example, citrus fruit, peppers or tomatoes) helps absorption. Tea and coffee can reduce iron absorption, so it may help to drink them between meals rather than with them. Exercise should be gentle to moderate while you are being investigated. If you feel breathless or dizzy, stop and rest, and mention it to your doctor.

Mental health and emotional wellbeing

Persistent tiredness and breathlessness can wear you down, and waiting for test results can be an anxious time. It is completely normal to feel worried or low. Talking to friends, family or your healthcare team often helps. If low mood or anxiety is affecting your daily life, tell your doctor — support is available, and you do not have to cope alone. If you ever feel unable to cope or have thoughts of harming yourself, contact your local emergency number or a crisis support service in your country straight away.

Prevention

Not all abnormal hematocrit results can be prevented, because some causes are genetic or linked to other illnesses. But many of the common causes can be reduced. Eating a varied diet with enough iron, vitamin B12 and folate, staying hydrated, not smoking and treating conditions such as sleep apnea all help keep your blood healthy. If you have heavy periods or a long-term condition that affects your blood, regular check-ups can catch changes early.

Screening programmes

There is no general screening programme for hematocrit alone. However, hematocrit is included in a full blood count, which is often checked as part of routine care for long-term conditions, during pregnancy, before some operations, and when you have symptoms such as tiredness. If you are in a group at higher risk, ask your doctor whether a blood count would be worthwhile.

Complications

If left untreated

• Ongoing low hematocrit can leave you persistently tired and short of breath, affecting work, study and daily life
• The heart has to work harder, which can worsen existing heart conditions or cause an irregular heartbeat
• In pregnancy, untreated anemia can affect both mother and baby, so it is important to have it checked
• Continued bleeding may go unnoticed if low hematocrit is not investigated
• Very high hematocrit makes the blood thicker, which can raise the risk of clots, stroke or other circulation problems
• Rarely, an abnormal result can be the first sign of a blood or bone marrow condition that needs specialist care

Long-term outlook

The outlook is usually very good. Most abnormal hematocrit results have a treatable cause, such as iron deficiency or dehydration, and improve with simple steps. Many people need only a repeat test and some dietary advice. If a more complex cause is found, early diagnosis means treatment can start sooner, and specialist teams have a lot of experience in managing these conditions. Keep your follow-up appointments and raise any worries with your healthcare team — they are there to help.

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