What is Hematocrit Test? Purpose, Levels, Procedure & Results

A hematocrit test measures the percentage of red blood cells in your blood. Think of it as checking how much of your blood is made up of the cells that carry oxygen throughout your body.

This simple blood test gives your doctor valuable information about your overall health. It helps detect conditions like anemia, dehydration, or blood disorders that might be affecting how well your body delivers oxygen to your tissues.

What is hematocrit test?

Hematocrit is the proportion of red blood cells compared to the total volume of your blood. When you spin a tube of blood in a centrifuge, the red blood cells settle to the bottom, and the hematocrit measures what percentage they make up.

The test is usually expressed as a percentage. For example, if your hematocrit is 40%, it means 40% of your blood volume consists of red blood cells, while the remaining 60% is plasma and other blood components.

Normal hematocrit levels vary between men and women. Men typically have higher levels because they naturally produce more red blood cells due to hormonal differences.

Why is hematocrit test done?

Your doctor orders a hematocrit test to check for blood-related health conditions. It's one of the most common blood tests and often part of a complete blood count (CBC) during routine checkups.

The test helps diagnose anemia, which occurs when you don't have enough healthy red blood cells to carry oxygen effectively. It can also detect polycythemia, a condition where you have too many red blood cells.

Healthcare providers use this test to monitor your response to treatments for blood disorders. If you're receiving treatment for anemia or taking medications that affect blood production, regular hematocrit testing helps track your progress.

Sometimes the test reveals dehydration or overhydration. When you're dehydrated, your hematocrit may appear falsely elevated because there's less fluid in your blood.

What is the procedure for hematocrit test?

The hematocrit test involves a simple blood draw from a vein in your arm. The entire process takes just a few minutes and causes minimal discomfort.

A healthcare professional will clean the area with antiseptic and insert a small needle into your vein. You might feel a brief pinch or sting when the needle goes in, but most people find it quite tolerable.

The blood flows into a small tube attached to the needle. Once enough blood is collected, the needle is removed and a bandage is applied to the site.

Your blood sample is then sent to a laboratory where it's processed using a centrifuge. The spinning motion separates the different components of your blood, allowing technicians to measure the exact percentage of red blood cells.

How to prepare for your hematocrit test?

Most hematocrit tests require no special preparation on your part. You can eat, drink, and take your regular medications as normal before the test.

However, if your doctor orders additional blood tests along with the hematocrit, you might need to fast for 8-12 hours beforehand. Your healthcare provider will give you specific instructions if fasting is necessary.

It's helpful to stay well-hydrated before your test, as this makes it easier for the technician to find a vein. Drinking water also helps ensure your results accurately reflect your normal blood composition.

Wear comfortable clothing with sleeves that can be easily rolled up. This makes the blood draw process smoother and more comfortable for you.

How to read your hematocrit test?

Hematocrit results are reported as percentages, and normal ranges depend on your age and gender. For adult men, normal levels typically range from 41% to 50%, while adult women usually have levels between 36% and 44%.

Children and infants have different normal ranges that change as they grow. Newborns often have much higher hematocrit levels that gradually decrease during their first year of life.

Your results will be compared to these reference ranges, but remember that "normal" can vary slightly between different laboratories. Your doctor will interpret your results in the context of your overall health and any symptoms you might be experiencing.

A single abnormal result doesn't necessarily indicate a serious problem. Your doctor might recommend repeating the test or ordering additional tests to get a complete picture of your health.

How to fix your hematocrit level?

Treatment for abnormal hematocrit levels depends entirely on the underlying cause. If your levels are low due to iron deficiency anemia, your doctor might recommend iron supplements or dietary changes to include more iron-rich foods.

For low hematocrit caused by chronic conditions like kidney disease, treating the underlying condition often helps improve your blood cell production. This might involve medications that stimulate red blood cell production or addressing nutritional deficiencies.

High hematocrit levels might require different approaches. If dehydration is the cause, increasing your fluid intake can help normalize your levels. For conditions like polycythemia vera, your doctor might recommend treatments to reduce red blood cell production.

Some people with high hematocrit may need therapeutic phlebotomy, where blood is regularly removed to reduce the concentration of red blood cells. This is similar to blood donation but done for medical reasons.

What is the best hematocrit level?

The best hematocrit level for you falls within the normal range for your age and gender. There's no single "perfect" number that applies to everyone, as individual factors can influence what's optimal for your health.

For most adults, hematocrit levels in the middle of the normal range indicate good health. Levels that are too low can lead to fatigue and weakness, while levels that are too high can increase your risk of blood clots.

Your ideal hematocrit level also depends on your lifestyle and health conditions. Athletes might naturally have slightly higher levels due to their body's adaptation to increased oxygen demands.

People living at high altitudes often have higher hematocrit levels because their bodies produce more red blood cells to compensate for lower oxygen levels in the air.

What are the risk factors for low hematocrit?

Several factors can increase your risk of developing low hematocrit levels. Understanding these risk factors can help you and your doctor identify potential causes and take preventive measures.

Nutritional deficiencies represent some of the most common risk factors. Iron deficiency is particularly important because iron is essential for red blood cell production. Women of childbearing age face higher risk due to menstrual blood loss.

Here are the main risk factors that can lead to low hematocrit:

• Heavy menstrual periods or frequent blood loss
• Poor dietary intake of iron, vitamin B12, or folate
• Chronic kidney disease affecting red blood cell production
• Inflammatory conditions like rheumatoid arthritis
• Certain medications that affect blood cell production
• Pregnancy, which increases blood volume and iron needs
• Gastrointestinal conditions that impair nutrient absorption
• Cancer or cancer treatments like chemotherapy
• Bone marrow disorders that affect blood cell production

Some rare conditions can also contribute to low hematocrit. These include genetic disorders affecting hemoglobin production, autoimmune conditions that destroy red blood cells, and certain infections that suppress bone marrow function.

What are the risk factors for high hematocrit?

High hematocrit levels can develop due to various factors, some of which are temporary while others represent ongoing health conditions. Identifying these risk factors helps your doctor determine the best treatment approach.

Dehydration is one of the most common causes of temporarily elevated hematocrit. When you lose fluids through sweating, vomiting, or diarrhea, your blood becomes more concentrated, making the hematocrit appear higher.

Several factors can increase your risk of developing high hematocrit levels:

• Living at high altitudes where oxygen levels are lower
• Smoking, which reduces oxygen delivery to tissues
• Chronic lung diseases that impair oxygen absorption
• Heart conditions that affect blood circulation
• Sleep apnea causing intermittent oxygen deprivation
• Certain medications like testosterone therapy
• Polycythemia vera, a bone marrow disorder
• Severe dehydration from any cause
• Kidney tumors that produce excess erythropoietin

Rare conditions that can cause high hematocrit include genetic mutations affecting oxygen sensing, certain brain tumors, and some inherited heart defects. These conditions are uncommon but require specialized treatment when present.

Is it better to have high or low hematocrit?

Neither high nor low hematocrit is better – the goal is to maintain levels within the normal range for your age and gender. Both extremes can cause health problems and indicate underlying conditions that need attention.

Low hematocrit means your blood can't carry oxygen as effectively as it should. This leads to fatigue, weakness, and shortness of breath because your tissues aren't getting enough oxygen to function properly.

High hematocrit makes your blood thicker and more likely to form clots. This increases your risk of serious complications like stroke, heart attack, or blood clots in your legs or lungs.

The ideal situation is having hematocrit levels that allow your blood to carry oxygen efficiently while flowing smoothly through your blood vessels. This balance supports optimal organ function and overall health.

What are the possible complications of low hematocrit?

Low hematocrit can lead to several complications if left untreated. The reduced oxygen-carrying capacity of your blood affects how well your organs function, potentially causing both immediate symptoms and long-term health issues.

The most common complications stem from your body's inability to deliver adequate oxygen to tissues. Your heart may work harder to pump blood, potentially leading to heart problems over time.

Here are the main complications associated with low hematocrit:

• Severe fatigue and weakness that interferes with daily activities
• Shortness of breath, especially during physical activity
• Rapid or irregular heartbeat as your heart works harder
• Difficulty concentrating and memory problems
• Increased risk of infections due to weakened immune system
• Restless leg syndrome and sleep disturbances
• Heart failure if the condition is severe and prolonged
• Delayed wound healing and recovery from illness
• Complications during pregnancy for both mother and baby

Rare but serious complications can include heart enlargement from constantly working harder to pump blood, and in extreme cases, organ damage from prolonged oxygen deprivation. Children with severe low hematocrit may experience developmental delays.

What are the possible complications of high hematocrit?

High hematocrit creates thick, viscous blood that doesn't flow as easily through your blood vessels. This increased thickness significantly raises your risk of developing dangerous blood clots throughout your body.

The complications of high hematocrit are often more immediately life-threatening than those of low hematocrit. The risk of cardiovascular events increases substantially when hematocrit levels remain elevated.

The primary complications you might face with high hematocrit include:

• Blood clots in your legs (deep vein thrombosis)
• Pulmonary embolism when clots travel to your lungs
• Stroke due to clots blocking blood flow to your brain
• Heart attack from clots in coronary arteries
• High blood pressure from increased blood viscosity
• Headaches and dizziness from poor circulation
• Vision problems due to blood vessel changes in your eyes
• Bleeding disorders despite thick blood
• Gout from increased breakdown of red blood cells

Less common but serious complications include kidney problems from poor blood flow, liver enlargement, and in rare cases, transformation to leukemia in people with certain blood disorders. Some people may also experience itching, especially after warm baths or showers.

When should I see a doctor for hematocrit test?

You should see a doctor if you experience persistent symptoms that might indicate abnormal hematocrit levels. Many people don't realize they have a problem until symptoms become noticeable in their daily lives.

For low hematocrit, watch for ongoing fatigue that doesn't improve with rest, unusual shortness of breath during normal activities, or pale skin and nail beds. These symptoms warrant medical evaluation even if they seem mild.

Signs that suggest you need medical attention include:

• Extreme fatigue that interferes with work or daily activities
• Shortness of breath during routine tasks
• Rapid heartbeat or chest pain
• Unusual paleness of skin, lips, or nail beds
• Frequent headaches or dizziness
• Cold hands and feet despite warm temperatures
• Difficulty concentrating or memory problems
• Heavy menstrual periods or unusual bleeding
• Persistent leg pain or swelling

Seek immediate medical care if you experience severe symptoms like chest pain, difficulty breathing, sudden severe headache, or signs of stroke. These could indicate serious complications requiring emergency treatment.