Nutrient & Blood Tests: Biomarkers, Reference Ranges & Scientific Basis
Nutrient and blood tests measure specific biomarkers in the blood—such as 25-OH-Vitamin-D3 for vitamin D status or ferritin as an iron store. Unlike genetic tests, they show current nutritional status and are assessed against established reference values from WHO, DGE, and EFSA. An abnormal value is an indication for preliminary evaluation, not a diagnosis, and should be medically assessed if symptoms are present.
What nutrient and blood tests are scientifically about
A nutrient or blood test measures so-called biomarkers—measurable substances in the blood that reflect nutritional or metabolic status. Examples include 25-OH-Vitamin-D3 as the storage form of vitamin D, ferritin as a measure of iron stores, or transcobalamin as the active fraction of vitamin B12. Unlike a genetic test, which describes a predisposition, a blood test shows a snapshot of the actual current state. A common reason for testing nutrient levels is persistent fatigue, for which medical guidelines recommend targeted, step-by-step evaluation [6].
The measured values are compared with reference ranges derived from professional societies and authorities—for example, the World Health Organization (WHO) for ferritin, the German Nutrition Society (DGE) for vitamin D, or the European Food Safety Authority (EFSA) for trace elements. These reference values are statistically defined ranges for healthy population groups, not individual target values.
The mybody® VitalCheck test uses capillary blood from the fingertip, collected at home and analyzed in a specialized laboratory. This page explains which biomarkers are measured, which reference sources the evaluation is based on, how the sample is processed, and where the limitations lie.
Overview of measured biomarkers
| Biomarker | What it is | Why it matters | Reference/evaluation basis |
|---|---|---|---|
| 25-OH-Vitamin-D3 | Storage form of vitamin D in the blood. | Most informative marker of vitamin D status; relevant for bones and muscles. | DGE reference values [2] |
| Ferritin | Iron-storage protein. | Most important single marker of iron stores; low levels indicate iron deficiency. | WHO guideline 2020 [1] |
| Vitamin B12 & Transcobalamin | Total B12 and the active fraction bound to transcobalamin (Holo-TC). | Holo-TC is considered an early marker of B12 deficiency, before total B12 levels fall. | Nexo & Hoffmann-Lücke 2011 [3] |
| Folic acid (folate) | Vitamin B9, important for blood formation and cell division. | Complements B12 when assessing B-vitamin status. | DGE/DACH reference values [7] |
| Calcium · Magnesium · Sodium | Macronutrients (electrolytes). | Involved in bone, muscle, and nerve function as well as fluid balance. | DGE/DACH reference values [7] |
| Zinc · selenium · copper · manganese | Trace elements. | Cofactors for numerous enzymes, including those involved in the immune system and cell protection. | EFSA reference values [4] |
| HDL · LDL · triglycerides | Blood lipids (lipid profile). | Established markers for assessing cardiovascular risk. | ESC/EAS Guideline 2019 [5] |
VitalCheck Complete includes 15 biomarkers, while VitalCheck Basic includes 7. Reference ranges may vary depending on the laboratory and method; the range stated in the report is always authoritative.
The biomarkers in detail
Vitamin D (25-OH vitamin D3)
The blood value 25-OH vitamin D3 (25-hydroxyvitamin D) is the recognized measure of vitamin D status because it reflects the storage form. The DGE has defined reference values for this [2]. Vitamin D is important for bone metabolism and muscle function; inadequate intake is common during the winter months at northern latitudes.
Ferritin (iron stores)
Ferritin is the storage protein for iron and the most important single marker of iron status. In 2020, the WHO published a guideline on ferritin thresholds for assessing iron status [1]. Low ferritin indicates depleted iron stores; since ferritin also rises with inflammation, it should be assessed in context.
Vitamin B12 and transcobalamin (Holo-TC)
Vitamin B12 is measured as a total value and via transcobalamin. The fraction bound to transcobalamin—holotranscobalamin (Holo-TC, “active B12”)—is considered an early marker of B12 deficiency, often declining before total B12 becomes abnormal [3]. The combination increases the informative value of the B12 assessment.
Folic acid and B-vitamin status
Folic acid (folate, vitamin B9) is needed for blood formation and cell division and is assessed together with B12. The reference values of the DGE and DACH professional societies provide the basis for assessment [7]. An isolated value is less informative than the overall picture from B12, holo-TC, and folate.
Macrominerals: calcium, magnesium, sodium
Calcium, magnesium, and sodium are electrolytes with functions in bones, muscles, nerves, and fluid balance. Their reference values are defined by the DGE/DACH professional societies [7]. Blood levels do not always reflect total body stores because the body tightly regulates these levels.
Trace elements: zinc, selenium, copper, manganese
Trace elements act as cofactors for many enzymes, including those involved in immune function and protection against oxidative stress. EFSA has derived Dietary Reference Values for these nutrients [4]. Because their levels are tightly regulated, an individual value is always assessed in its clinical context.
Blood lipids: HDL, LDL, triglycerides
The lipid profile comprising HDL cholesterol, LDL cholesterol, and triglycerides is used to assess cardiovascular risk. The 2019 European ESC/EAS guidelines define the basis for assessment and risk-dependent target ranges [5]. Individual assessment—for example, of the LDL target value—depends on overall risk and should be handled by a physician.
Data protection, methodology & quality
Data protection & data processing: Protecting your data is our top priority. Under the General Data Protection Regulation (GDPR), health data are considered special categories of personal data requiring particular protection (Article 9 GDPR). At mybody®, your data is processed for a specific purpose—solely to perform and evaluate your test—and on the basis of your consent. It will not be processed further for other purposes without your consent.
Information security is organized in accordance with ISO/IEC 27001, the internationally recognized standard for information security management systems. Your data is transmitted and stored in encrypted form. You have the rights of data subjects under the GDPR—particularly the rights to access, rectification, and erasure of your data. Details regarding storage periods, processing, and your rights are set out in the privacy policy.
The sample is collected at home as capillary blood from the fingertip. After it is returned, the sample is analyzed in a medical laboratory using established laboratory medicine methods (clinical chemistry/immunoassay). The measured values are assessed against the reference ranges stated in the report.
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1
Collect sample
Capillary blood collected at home via fingertip (test kit including instructions).
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2
Return shipping
Free return shipping to the analysis laboratory.
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3
Laboratory analysis
Analysis of biomarkers using established measurement methods.
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4
Evaluation
Assessment against reference values and preparation of the laboratory report.
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5
Result
Available in the online portal; 3–5 business days after receipt of the sample.
Capillary blood: convenient at home—and scientifically comparable
The practical advantage of the method lies in self-collection. Just a few drops of capillary blood from the fingertip are sufficient for the sample and can be collected at home without a doctor’s appointment or venous blood draw. This lowers the barrier to an initial assessment—for example, with a busy schedule or reluctance to undergo venipuncture. The actual analysis is then performed by the specialist laboratory using the same quantitative measurement methods as for venous blood.
The validity of the results has been demonstrated for key markers: A 2024 study showed good agreement between capillary and venous blood for 25-OH vitamin D3 (Kappa value 0.75) and described a conversion formula between the two collection methods [10]. Fingertip sampling is therefore suitable for an indicative status assessment and for monitoring changes over time. Correct collection according to the instructions remains essential; methodological limitations are described in the next section.
Laboratory & accreditation: The blood analysis is carried out in a medical laboratory accredited according to DIN EN ISO 15189:2024 (MVZ GANZIMMUN GmbH, Mainz; DAkkS registration number D-ML-13151-01-00) [8]. The laboratory participates in external proficiency testing schemes (including INSTAND e.V., Referenzinstitut für Bioanalytik/RfB, UK NEQAS, and ERNDIM). Accredited refers to the assessment of the technical competence of the analysis by the German Accreditation Body (DAkkS) [9] and must be distinguished from certified (proof of a management system, such as ISO 9001 or ISO/IEC 27001).
What these tests cannot do
- Not a diagnosis. An abnormal value is an indication for preliminary evaluation and does not replace medical diagnosis or treatment.
- Only a snapshot. Blood values fluctuate over time and depending on the time of day and diet. A single measurement does not reflect a permanent state.
- Reference ranges are not individual. They apply to population groups and vary depending on the laboratory, method, age, and sex; a value just outside the range is not automatically pathological.
- Capillary blood has methodological limitations. Individual parameters may differ from those obtained from a venous blood draw; preanalytics (correct collection) influence the result.
- When medical evaluation is necessary. Medical advice should be sought in the case of clearly abnormal values, persistent symptoms, during pregnancy or breastfeeding, or before starting supplementation.
Frequently asked questions
Are nutrient blood tests from the fingertip reliable?
For many parameters, capillary blood from the fingertip provides useful results when the sample is collected correctly and analyzed in a specialized laboratory. Individual values may differ slightly from those obtained from a venous blood draw. Standardized analysis and evaluation against the reference range stated in the report are crucial.
What is the difference between a nutrient test and a DNA test?
A nutrient blood test measures the current nutritional status—that is, how much of a substance is currently present in the blood. A DNA test, by contrast, describes a genetic predisposition, independently of the value on a given day. For the question “do I currently have a deficiency?”, a blood test is the right approach.
What does the ferritin value indicate?
Ferritin is the storage protein for iron and the most important single marker of iron stores. A low value indicates depleted iron reserves. Since ferritin can increase during inflammation, it is assessed in conjunction with other information; the WHO has defined thresholds for this.
Why are vitamin B12 and transcobalamin measured together?
Transcobalamin transports the active fraction of vitamin B12 available to cells (holo-TC). This fraction often decreases earlier than total B12 in the event of a deficiency. Measuring both therefore improves early assessment of B12 status.
Where do the reference values come from?
The assessment is based on established sources: the WHO for ferritin, the DGE for vitamin D and other nutrients, the EFSA for trace elements, and the ESC/EAS guideline for blood lipids. These reference ranges apply to population groups and are not individual target values.
Does a self-test (rapid test) replace laboratory analysis?
No. A rapid home test in the form of a test cassette provides an initial indication within minutes, for example in a vitamin D or ferritin self-test. A quantitative laboratory analysis such as VitalCheck, on the other hand, measures specific values. For a reliable assessment, the laboratory analysis is more informative.
When should I have the results evaluated by a doctor?
Medical advice is advisable in the case of significantly abnormal results, persistent symptoms such as fatigue, during pregnancy or breastfeeding, and before planned supplementation. The test is intended for preliminary assessment and preparation for a consultation, not for self-treatment.
How quickly are the results available, and how is my data protected?
The laboratory analysis usually takes 3–5 business days after the sample arrives; the evaluation is then made available in the online portal. Processing complies with the GDPR, the information security management system is established in accordance with ISO/IEC 27001, and health data is transmitted in encrypted form.
Sources
- World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva, 2020. who.int
- German Nutrition Society (DGE). Reference values for nutrient intake: Vitamin D. dge.de
- Nexo E, Hoffmann-Lücke E. Holotranscobalamin, a marker of vitamin B-12 status: analytical aspects and clinical utility. Am J Clin Nutr 2011;94(1):359S–365S. PMC
- European Food Safety Authority (EFSA). Dietary Reference Values for nutrients (including zinc, selenium, and copper). efsa.europa.eu
- Mach F et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias. Eur Heart J 2020;41(1):111–188. Eur Heart J
- DEGAM S3 Guideline “Fatigue”, AWMF Reg. No. 053-002, 2023 version. register.awmf.org
- German Nutrition Society (DGE). Reference values for nutrient intake (DACH), including folate, calcium, and magnesium. dge.de
- MVZ GANZIMMUN GmbH. Quality management – accreditation according to DIN EN ISO 15189:2024 (DAkkS D-ML-13151-01-00). ganzimmun.de
- DAkkS – Medical Laboratories / DIN EN ISO 15189 (accreditation explanation). dakks.de
- Xing Y et al. Correlation and consistency between two detection methods for serum 25-hydroxyvitamin D levels in human venous blood and capillary blood. Front Nutr 2024;11:1291799. Frontiers in Nutrition
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