Defining deficiencies through tests is one of the most challenging tasks. The main mistake is trying to measure vitamins directly and draw conclusions from a single number. In practice, most vitamin tests do not reflect the actual situation in tissues.
The body can maintain the levels of substances in the blood even with a pronounced deficiency by redistributing resources. Therefore, it is important to use indirect markers for assessing the state.
Why direct vitamin tests are often useless
Direct serum values for B12 and folate need especially careful interpretation after recent supplement use. A blood level can confirm that the nutrient reached the bloodstream, but it does not automatically show how well it reaches tissues or enters the enzyme systems that actually need it.
If B12 is technically within range but there is numbness, fatigue, high MCV, elevated homocysteine, or long-standing digestive problems, deficiency should not be dismissed too early. In that situation it is more useful to look at the whole picture: diet, stomach acid, metformin or proton pump inhibitors, gut health, and red blood cell indices.
The level of vitamins in the blood is not their reserve and not the efficiency of their use.
It can be normal in cases of:
- poor absorption;
- transport disorders;
- enzyme defects;
- increased consumption.
Example:
- vitamin B12 — normal;
- homocysteine — elevated;
This indicates a functional deficiency: the vitamin is present in the blood but is not working in metabolism.
Ferritin — the main marker of iron deficiency
Ferritin reflects the iron reserves in the body, not just its level in the blood. It is one of the most reliable indicators of deficiency.
Example: ferritin — 15–30 ng/ml. This already indicates a state of deficiency, even if hemoglobin remains normal.
Another example:
- ferritin — 80–120;
- there is fatigue;
In this case, inflammation needs to be considered, as ferritin can increase as an acute phase protein.
Homocysteine — a universal marker of deficiencies
Homocysteine shows how effectively methylation processes, which depend on B vitamins, are working. An increase in this indicator is one of the first signs of hidden deficiencies.
Example: homocysteine — 10–14 µmol/L. This is already a signal of a disorder, even if B12 and folic acid are normal.
Optimal values: 6–8 µmol/L. This indicates effective metabolism.
Indirect markers of B vitamins
For B vitamins, combinations matter more than a single isolated number. Elevated homocysteine often points not only toward B12 and folate, but also toward vitamin B6 and riboflavin because they also participate in one-carbon metabolism and in enzyme systems related to blood formation and energy production.
That is why the combination of MCV, MCH, ferritin, homocysteine, and symptoms is usually more informative than a long list of “serum vitamin” results. It helps separate low stores from transport problems and from situations where nutrients are present in blood but are not being used efficiently in tissues.
B vitamins are involved in hematopoiesis. Therefore, their deficiency is reflected in blood indicators.
Key markers:
- MCV — mean corpuscular volume;
- MCH and MCHC — hemoglobin content;
- homocysteine.
Example:
- MCV is elevated;
- homocysteine is high;
This is a sign of B vitamin deficiency, even without direct tests.
Another example:
- MCV is decreased;
- ferritin is low;
This indicates iron deficiency.
Omega-3 index — a marker of membrane condition and inflammation
The Omega-3 index shows the content of EPA and DHA in cell membranes. It is not just a fat indicator, but an indicator of:
- inflammatory processes;
- nutritional quality;
- cell condition.
Example: Omega-3 index — below 4%. This indicates a high risk of inflammation and deficiency.
Optimal values: 8–12%. This indicates a stable condition.
How to combine all indicators
To understand deficiencies, it is important to look at the system:
- ferritin — iron reserves;
- homocysteine — efficiency of metabolism;
- erythrocyte indices — hematopoiesis;
- Omega-3 — cell condition.
Example of a comprehensive picture:
- ferritin — 22;
- homocysteine — 11;
- MCV — elevated;
- Omega-3 index — 3.5%;
This combination indicates a systemic deficiency: iron, B vitamins, and fatty acids.
Common mistakes:
- focusing only on vitamin tests;
- ignoring homocysteine;
- assessing iron by hemoglobin;
- not analyzing erythrocyte indices;
- ignoring the Omega-3 index.
Main principle. Deficiencies are not the absence of a substance in the blood but a disruption in its utilization.
Therefore, indirect markers often provide more information than direct tests. Only a systemic approach allows us to see real problems before pronounced symptoms appear.
