- The test strip is a small laboratory for exactly one measurement.
- An enzyme in the strip reacts with the lactate in the blood. This makes a tiny current flow.
- The device measures this current and converts it into mmol/L.
- What makes the value reliable is clean sampling, a suitable environment and correctly stored strips.
A drop of blood, a ten-second wait, a number on the display. What happens in between is quickly explained and helps you avoid measurement errors.
The path of the drop
Metabol Pro and Lactate Express work on the same principle: an electrochemical biosensor. The actual measurement takes place in the test strip.
The drop is drawn in
You hold the tip of the strip to the drop of blood. A fine channel draws the blood in by itself. For lactate, 0.8 µL is enough.
The enzyme reacts
The reaction zone contains an enzyme, lactate oxidase. It converts the lactate in the blood sample.
A current flows
This reaction produces a tiny electric current. How strong it is depends on how much lactate the sample contains.
The device converts the current
The meter measures the current and calculates the lactate concentration from it. After 10 seconds the value appears on the display.
What the code chip is for
Test strips are manufactured in lots, and each lot reacts very slightly differently. That is why every box comes with a code chip. It tells the device how to convert the measured current into a lactate value for exactly these strips.
A simple rule follows from this: chip and strips belong together. When you open a new box, you change the chip as well. The code on the display must match the code on the strip vial.
What the number on the display means
The result is the lactate concentration in your blood in millimoles per litre (mmol/L). The devices measure in the range from 0.5 to 28.0 mmol/L. If a value lies outside this range, the Lactate Express shows “LO” or “HI”.
How to put the value into context is explained in Chapter 1. For training, what counts above all is the trend across several stages, not the single number.
How reliable is a handheld meter?
A handheld meter works with a drop of whole blood, right where the training takes place. A laboratory analyser works with a prepared sample under fixed conditions. Both measure the same thing, but not in the same way. Small differences between devices are therefore normal.
For the Lactate Express there is an independent study on this (Meixner et al., Biology Open 2026). In the range from 1 to 4 mmol/L, the values agreed well with the laboratory analyser. This is the range in which the thresholds lie. At higher concentrations, the handheld device showed lower values on average than the laboratory analyser.
Control solution: the system check
A control solution is a liquid with a known lactate content. You apply it to a test strip instead of blood. If the result lies within the range stated on the control solution packaging, device and strips are working together correctly.
The control solution checks the system; it does not adjust it. Adjusting the device to the lot is done by the code chip alone. The check is useful, for example, when values seem implausible to you.
What interferes with the measurement
- Temperature and humidity: Lactate measurement requires 15 to 35 °C and 10 to 85% relative humidity. If device and strips have come out of a cold car, give them time.
- Open vial: Test strips absorb moisture. Close the vial immediately after taking a strip out.
- Old strips: Check the expiry date. Once opened, lactate test strips can be used for three months.
- Wrong code: A chip and strips from different boxes give incorrect values.
- Too little blood: If the reaction zone is not filled, take a new strip.
- Careless sampling: Sweat and squeezing are the most common sources of error. More on this in the next chapter.
The instructions for use supplied with your device and the test strips are authoritative for how to use them. Source of the study: Meixner B et al. (2026), Biology Open 15, bio062543, doi:10.1242/bio.062543.