Haematocrit and altitude training: does your haematocrit really go up?
Published 21 August 2012 · 7 min read
One of the most frequently asked questions about altitude training is whether your haematocrit actually increases. This is logical. Many athletes directly associate a higher haematocrit with better performance, increased oxygen transport, and greater endurance.
However, the reality is slightly more nuanced. An increase in haematocrit can occur during altitude training, but it is not the most important parameter to look at. Furthermore, a higher haematocrit does not automatically mean you have produced more red blood cells.
In this article, you will discover when haematocrit rises, why it happens, which blood values are more relevant, and how to objectively assess whether altitude training actually had an effect.
Short answer:
- Yes, haematocrit can rise during altitude training.
- The increase isn't always due to extra red blood cells.
- Loss of plasma volume can temporarily increase haematocrit.
- Haemoglobin, reticulocytes and total red blood cell mass are often more informative.
- For sports performance, oxygen transport capacity ultimately counts, not just haematocrit percentage.
Conclusion: haematocrit often rises during altitude training, but doesn't tell the full story.
Nuance: A higher value can arise from both adaptation and moisture changes.
Practical hook: Always look at multiple markers and trends instead of a single blood value.
Wat is hematocriet precies?
Haematocrit indicates the percentage of your blood that consists of red blood cells. For example, if a laboratory reports a haematocrit of 45%, this means that 45% of the blood volume consists of red blood cells and 55% consists of plasma and other components.
As red blood cells are responsible for oxygen transport, haematocrit is often used as an indirect indicator of the body's oxygen-carrying capacity.
That sounds simple, but there's an important limitation to this value. Haematocrit is a ratio. Because of this, the value can rise without you actually having produced more red blood cells.
📊 Research shows that changes in plasma volume are sometimes more apparent than changes in red blood cell mass. As a result, haematocrit can temporarily increase without a genuine increase in oxygen transport capacity.
Why does haematocrit rise during altitude training?
When you stay in an environment with less oxygen, the body reacts almost immediately. The kidneys produce more EPO, a hormone that stimulates the production of red blood cells.
This process is discussed extensively in our article on The natural rise in EPO during altitude training.
Over time, this can lead to the production of extra red blood cells. Because red blood cells transport oxygen, this can contribute to improved aerobic performance capacity.
At the same time, something else often happens. During the first few days at altitude, plasma volume often decreases, making the blood relatively more concentrated. This also contributes to a higher haematocrit value.
A rise in haematocrit can therefore have two causes:
- more red blood cells
- less plasma volume
In practice, it is usually a combination of both.
Haematocrit versus red blood cell mass
Many athletes look exclusively at haematocrit. This is understandable, but scientifically speaking, total red blood cell mass is a much stronger indicator.
| Parameter | What does it measure? | Practical value |
|---|---|---|
| Haematocrit | Percentage of red blood cells in blood | Quick indication, sensitive to moisture status |
| Haemoglobin | Oxygen-carrying protein | Important for oxygen transport |
| Reticulocytes | Young red blood cells | Shows recent creation |
| Red blood cell mass | Total red blood cell count | Best indicator for adaptation |
Measurement: Percentage of red blood cells
Value Sensitive to moisture status
Measurement: Oxygen-carrying protein
Value Important for oxygen transport
Measurement: Young red blood cells
Value Recent blood donation
Measurement: Total red blood cell count
Value Best fit for adaptation
You see a rise in haematocrit when there is dehydration.
The rate at which haematocrit changes varies greatly from person to person.
Factors involved include:
- the altitude at which you are staying
- the number of hours of exposure per day
- the total duration of the programme
- Iron status and ferritin levels
- Genetic predisposition to hypoxia
In a classic sleep high, train low With protocols, effects often become visible after a few weeks. This is why many athletes opt for exposure of at least three to four weeks.
In practice, we often see athletes noticing changes in recovery, resting heart rate, and training feel before clear blood value changes become apparent.
Yes, a high haematocrit can also have disadvantages.
Yes. An extremely high haematocrit is not automatically positive.
Naarmate the blood thickens, its viscosity also increases. This means the heart has to work harder to pump blood around.
With normal altitude training regimens, this rarely poses a problem. However, it is one of the reasons why professional sports programmes often monitor multiple blood values rather than solely haematocrit.
The goal is not to achieve the highest possible value. The goal is to develop a more efficient oxygen transport system without unnecessary strain.
For athletes, the most interesting blood values are usually related to: * **Red Blood Cells:** Haemoglobin and haematocrit (to check for anaemia and oxygen-carrying capacity). * **Iron Status:** Ferritin, transferrin, and transferrin saturation (essential for red blood cell production and energy metabolism). * **Muscle Damage/Enzymes:** Creatine kinase (CK) and lactate dehydrogenase (LDH) (to monitor muscle stress and recovery). * **Electrolytes:** Sodium, potassium, chloride, and magnesium (important for hydration, muscle function, and nerve signalling). * **Kidney Function:** Creatinine and urea (to assess kidney health, especially with high protein intake or intense training). * **Liver Function:** ALT, AST, and bilirubin (to check for any strain on the liver). * **Lipid Profile:** Cholesterol (total, HDL, LDL) and triglycerides (for overall cardiovascular health and energy). * **Hormones:** Testosterone, cortisol, and possibly thyroid hormones (to gauge hormonal balance, stress, and recovery). * **Vitamin D:** Important for bone health, immune function, and muscle performance. * **B12 and Folate:** Crucial for energy metabolism and red blood cell production.
Those serious about altitude training may consider monitoring other markers besides haematocrit.
- haemoglobin
- ferritin
- reticulocytes
- red blood cell count
- Transferrin saturation
Especially iron status plays an important role. Without sufficient iron, the production of new red blood cells is limited, even when the body produces extra EPO.
Therefore, also read our article about iron and nutrition during altitude training.
How to monitor this objectively
A successful altitude training programme is not assessed on the basis of a single blood value.
| Factor | What are you paying attention to? | Decision rule |
|---|---|---|
| SpO₂ trend | Multi-day morning trend | Trend more important than isolated measurement |
| Sleep | Depth and continuity | Persistent disruption = potential adjustment |
| Recovery | Fatigue and training sensation | Negative trend requires evaluation |
| Blood values | Haemoglobin, ferritin, haematocrit | Always interpret in context |
Focus: Morning trend
Decision rule: Look at multiple days
Focus: Sleep quality
Decision rule: When prolonged disruption occurs, evaluate
Focus: Tiredness and feeling
Decision rule: Investigate negative trend
Focus: Haemoglobin, ferritin, haematocrit
Decision rule: Always assess in combination
Altitude training is useful for increasing haematocrit when the training is performed at altitudes of 2,000 metres or higher for a duration of at least four weeks.
Altitude training can be interesting when:
- You are an endurance athlete
- you are preparing for a high-altitude placement
- you are working towards a marathon, triathlon or cycling goal
- you have sufficient time for a multi-week programme
Less meaningful when:
- my ferritin levels are low
- you only have a few days available
- you exclusively focus on one blood value
Common misconceptions about haematocrit
A higher haematocrit reading always means better performance
No. Performance improvement depends on many factors, including training, recovery, nutrition, and oxygen transport.
Everyone reacts the same to altitude training
No. Some athletes respond strongly to hypoxia, while others show limited changes.
Only haematocrit counts
No. Haemoglobin, ferritin, and red blood cell mass often give a more complete picture.
FAQ
What is the average increase in haematocrit with altitude training?
This varies from person to person. Small increases are common, but the individual response varies greatly.
Is a blood test necessary?
No, but for athletes who want to measure objectively, it can provide valuable information.
How quickly does haematocrit rise?
Changes are often visible after a few weeks of consistent exposure to hypoxia.
Can a sleep tent increase haematocrit?
That can be. Especially when sufficient hours of exposure are combined with a well-constructed protocol.
Curious what altitude training could mean for your performance?
Do you want to specifically work on oxygen transport, endurance, and an optimal altitude training protocol? Explore the possibilities for athletes or read about the experiences of other athletes.
Conclusion
The question of whether haematocrit rises due to altitude training can be answered with a simple yes. However, that is only part of the story.
A higher haematocrit value can result from both extra red blood cells and changes in plasma volume. Therefore, it is advisable to combine multiple blood values and performance indicators.
For athletes who seriously employ altitude training, it ultimately isn't about one number on a blood test. It's about a better oxygen transport system, improved recovery, and a higher performance capacity for those moments that truly matter.
