Hematocrit

What is being measured

The hematocrit indicates what proportion of the blood volume the cells, in practice the red blood cells, take up. It is therefore a relationship, and a relationship has two sides: the cells at the top, the entire blood at the bottom. What moves value can come from both sides, and in everyday life it comes more often from below than from above.

What blood is made of and how oxygen transport works is explained below Blood. There are also figures on how often the value increases during testosterone treatment and what that means for the heart and blood vessels. The measurement itself has its own quirk, and that is the subject of what follows.

Reference range

• Men about 40 to 52 percent
• Women about 36 to 48 percent

Conventions of laboratory medicine, not study findings. They differ depending on the measurement method, the area depends on your own findings.

Why the same person has different values

The number of red blood cells changes over weeks and the plasma volume over hours. A hematocrit that is taken without preparation therefore sometimes measures something other than what it was taken for.

The posture

The change between lying and standing shifts fluid between the bloodstream and tissue, thereby changing plasma volume, hematocrit, hemoglobin and plasma proteins. These shifts were clear in the group examined with illnesses and smaller in the comparison subjects. The work therefore recommends standardizing the conditions before blood collection.

The training, in both directions

A systematic review of changes in plasma volume notes two opposing effects. Acute stress reduced plasma volume by 7 to 19.9 percent in both trained and untrained subjects in all included studies. Long-term training increased it by 6.6 to 16 percent in untrained people; for those who trained, the results were inconsistent.

Shortly thereafter, the acute effect is reversed. In the 24 hours after a session, the plasma volume increased by 7.3 percent after treadmill training and by 6.3 percent after the bicycle ergometer in a study of ten people; After intervals, the increase was similar at 4.2 to 6.6 percent.

In these studies, the plasma volume was measured, not the hematocrit. Because it is a proportion of the total blood, a smaller plasma volume results in a higher value and a larger one results in a lower value; The calculation is obvious, it is not measured there.

An observation on endurance athletes fits this direction: the mean hemoglobin values ​​were in the normal range in all groups and did not differ between athletes and comparison persons, and the lower values ​​there were interpreted as dilution due to an expanded plasma volume. A lack of red blood cells does not have to be the cause of a low value.

The liquid

The same mechanism in the other direction: those who lose weight dehydrated have less plasma and therefore a higher proportion of cells in it. This is the common explanation and follows from the structure of the value; A study that quantifies the effect on strength athletes is not included in the work used here.

What really lifts him up

A testosterone treatment, and it’s reliable. A review of the hematological effects of androgens calls erythrocytosis one of the most common side effects of testosterone treatment, with a relative risk of 8.14 compared to controls. A second overview puts the risk of a hematocrit above 52 percent as increased by 315 percent, or about four times, and notes that all dosage forms increase hemoglobin and hematocrit, the injectable ones the most.

This is consistent with an observation of 69 men taking testosterone undecanoate: in 21 of them, hemoglobin, hematocrit or erythrocytes were increased, a real increase in red blood cells was only present in a small proportion, and thrombosis did not occur in any of those affected.

• The dosage form counts. Injectable forms increase the value the most. For testosterone undecanoate, the median optimal injection interval in an observation of 325 patients was 12 weeks, with considerable variation between individuals.
• Sleep apnea is next to it, not underneath it. In a very small trial in five hypogonadal men, testosterone reduced hypoxic respiratory drive from 158 to 88; Obstructive sleep apnea developed new in one and worsened in another. The paper does not report a hematocrit finding; The path to a higher value via a nighttime lack of oxygen is suggested and not shown.
• Height and smoking are also considered causes. This is not proven in the works used here.

The sleepers and what they carry

The number circulating is 54 percent. It comes from a clinical handbook on managing erythrocytosis during testosterone treatment, which recommends reducing or suspending treatment from this level until the level normalizes. The Endocrine Society guideline lists hematocrit as one of the values ​​monitored during treatment.

This does not mean that the hematocrit value itself determines the risk of thrombosis, and this is controversial. An overview of non-JAK2-mutated erythrocytosis states that the current recommendations are not supported by hard evidence, that indiscriminate phlebotomy treatment is not recommended and that fears of thrombosis in this context are partly unfounded. The 54 is therefore an action threshold and not a measured risk limit. The comparison of the arguments is below Blood.

How to measure so that the number means something

• Always under the same conditions. Same time of day, same posture, sit for a few minutes before removal. The recommendation to standardize the conditions before acceptance is already in the work that described the husbandry effects.
• Drink normally. If you come to the weight loss when you are dehydrated, you measure your plasma volume and not your red blood cells.
• Not immediately after training and not the day after. Both times are in a phase in which the plasma volume moves, in opposite directions.
• The course beats the individual value. A value of 53 percent says little in itself; Three values ​​taken over six months under the same conditions say a lot.
• Together with Haemoglobin and red blood cells read. If all three move in the same direction, a change in the red row is closer; The hematocrit alone moves, rather the plasma. This has not been proven as a tested decision rule, and a volume effect shifts hemoglobin and hematocrit together anyway.

Classification

The hematocrit rightly has the reputation of being the value to keep an eye on during testosterone treatment: it increases reliably. What it lacks is reliability in individual values. It is a ratio whose denominator shifts with posture, fluidity and the last training session, and the magnitude of these shifts is precisely the range in which decisions are made.

This results in less than you think and something different. Less: a single 53 is not a finding. Other: several measurements under the same conditions are more effective than a single one, and that costs nothing apart from planning.

The core of the question remains open. The extent to which dehydration actually increases the value of a strength athlete is not quantified in the studies used here, and it is unclear whether the hematocrit value itself carries the risk of thrombosis or is only associated with it. Both affect the number on which the decision depends.

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