The Illusion of Normal: What Hides Behind Ideal Vitamin Blood Test Results

A lab report where all vitamin markers fall within the reference range creates a convincing illusion of wellbeing. Yet a person's actual state may not match what the paper shows: years of taking supplements and flawless test results, but persistent exhaustion, slow recovery, or unstable energy that simply won't go away.

When standard diagnostics offer no explanation, the problem is usually neither supplement quality nor laboratory error. It lies in the blind spot of the method itself. A blood test captures the concentration of a nutrient in plasma at the moment of sampling. But between "enough in the blood" and "the body is actually using it" there is a long route with four barriers — each of them linked to genetics.

On why supplements do not always deliver their expected effect — Why Vitamin Deficiency Is Not Always Solved by Supplements.

Stages of Bioavailability: Where Genetics Affects Absorption

A nutrient is not "absorbed" the moment you swallow it. Between ingestion and cellular use it must cross four sequential barriers:

1. capture by specific transport proteins in the wall of the small intestine;

2. delivery to tissues via lipoproteins and carrier proteins;

3. enzymatic conversion into the biologically active form;

4. binding to the cellular receptor.

Genetic variants at each of these stages determine the real-world efficiency of nutrient absorption — independently of the dose taken through food or a supplement (Vlieg-Boerstra et al., Nutrients, 2025). None of these barriers is visible in a standard blood test. Each of them is a distinct object of genetic analysis.

Water-Soluble Vitamins: Genetic Factors in Conversion and Metabolism

Vitamins B1, B3, and B5 support mitochondrial energy metabolism — from initiating the Krebs cycle to synthesising NAD+ and coenzyme A. Vitamin B6 is a cofactor in the synthesis of serotonin, dopamine, and GABA, but only in its active form, pyridoxal-5-phosphate; in some individuals this conversion is genetically slowed, even though a standard blood B6 level does not reflect this. Genetic variants of transport proteins and enzymes involved in energy metabolism and methylation reactions are associated with differences in the efficiency of these processes at tissue level (Vlieg-Boerstra et al., Nutrients, 2025).

For vitamins B9 and B12, the key gene is MTHFR (methylenetetrahydrofolate reductase), which converts folic acid into methylfolate — the active form required for the methylation cycle. The common variants rs1801133 (C677T) and rs1801131 (A1298C) reduce enzyme activity, lead to homocysteine accumulation, and lower the functional availability of methylfolate — even when blood folate levels are within range (Wójcik et al., Genes, 2024).

More on B vitamins and homocysteine — B Vitamins and Homocysteine: What a Standard Test Won't Show.

Vitamin C is transported into cells via sodium-dependent transporters SVCT1 and SVCT2, encoded by genes SLC23A1 (solute carrier family 23 member 1) and SLC23A2 (solute carrier family 23 member 2): their variants determine individual vitamin C requirements — the same dose produces different levels of tissue saturation in different people (Vlieg-Boerstra et al., Nutrients, 2025).

Fat-Soluble Vitamins: From Enzymatic Conversion to Receptor Sensitivity

Vitamin A reaches the body either directly from animal foods as retinol, or from plant sources through the enzymatic conversion of beta-carotene. This process is carried out by the gene BCO1 (beta-carotene oxygenase 1): variants rs12934922 and rs7501331 reduce enzyme activity, so a plant-based diet, even one rich in carotenoids, may not provide sufficient active vitamin A (Mwangangi et al., Front. Nutr., 2022).

Vitamin D acts through the receptor encoded by the gene VDR (vitamin D receptor). A 2022 systematic review and meta-analysis confirmed that the TaqI (rs731236) and FokI (rs10735810) polymorphisms determine the individual response to vitamin D supplementation — the same dose produces different increments of the active form depending on genotype (Usategui-Martín et al., Nutrients, 2022).

More on this — Vitamin D: Why a Universal Effective Dose Does Not Exist.

Vitamins E and K are absorbed as part of chylomicrons. Cellular uptake of vitamin E depends on the gene SCARB1 (scavenger receptor class B member 1): variants rs4238001 and rs11057830 are associated with differences in its circulating levels (Corrado et al., Int. J. Mol. Sci., 2025). Vitamin K activates osteocalcin via the enzyme encoded by the gene GGCX (gamma-glutamyl carboxylase): polymorphisms of GGCX are linked to a predisposition to reduced bone mineral density (Wu et al., Blood, 2021).

Mineral and Electrolyte Homeostasis: The Role of Transport Channels and Carrier Proteins

Magnesium is absorbed and reabsorbed in the kidneys via channels TRPM6 (transient receptor potential melastatin 6) and TRPM7 (transient receptor potential melastatin 7): the rs2274924 variant of TRPM6 is associated with a predisposition to lower serum magnesium and increased urinary excretion (Huang et al., Mol. Nutr. Food Res., 2023). Clinically this presents as persistent muscle cramps, difficulty falling asleep, and reduced stress resilience — even with consistent supplementation.

Calcium is absorbed via the enterocyte channel TRPV6 (transient receptor potential cation channel subfamily V member 6): its variants are linked to individual differences in bone mineralisation (Khattar et al., Gene, 2022). Iron is regulated by the gene HFE (homeostatic iron regulator): the C282Y (rs1800562) and H63D (rs1799945) polymorphisms are associated both with reduced bioavailability and with a predisposition to iron accumulation (Olynyk & Ramm, N. Engl. J. Med., 2022).

Sodium and potassium regulate blood pressure and neuromuscular conduction. Genetic sensitivity to sodium — including through polymorphisms of the gene ACE (angiotensin-converting enzyme) — determines whether restricting salt intake will actually lower blood pressure in a given individual (Raina et al., Front. Pediatr., 2022). Iodine, essential for thyroid function, is of particular relevance in Ukraine as an iodine-deficient region: genetic characteristics of iodine metabolism determine individual vulnerability to the consequences of insufficiency (Fedoniuk et al., Wiad. Lek., 2026).

Zinc is absorbed via the transporter SLC39A4 (solute carrier family 39 member 4): its variants are associated with differences in intestinal zinc absorption efficiency (Hennigar et al., J. Nutr. Biochem., 2022). For selenium, the key gene is SELENOP (selenoprotein P) — the primary plasma selenium transport protein: the rs3877899 polymorphism determines the individual response to dietary selenium intake (Outzen et al., Genes Nutr., 2018). Copper, molybdenum, and cobalt also have genetically determined metabolic characteristics that affect their functional availability.

When Genetic Context Changes the Logic of Decisions

A blood test and a genetic test answer different diagnostic questions. The first reflects current plasma nutrient levels; the second describes stable genetic mechanisms governing nutrient transport, conversion, and cellular utilisation. These two levels are not in competition — they complement each other, providing different layers of interpretation of nutrient status.

• Chronic fatigue without an obvious cause: when standard workups offer no explanation and vitamin levels in the blood are formally normal, genetic characteristics of B-vitamin, magnesium, or iron metabolism may provide the answer.

• Plant-based diet or strict dietary restrictions: vitamin B12, iron, zinc, calcium, vitamin A, and iodine are nutrients of concern in plant-based eating, and genetic characteristics of their absorption additionally affect functional availability.

• Preventive strategy from age 30: knowing individual nutrient metabolism characteristics makes it possible to act before deficiencies develop — particularly for B12 and vitamin D.

• Supplements taken without a measurable effect: a genetic profile can explain whether selecting active forms or adjusting dosages in consultation with a doctor is warranted.

The Vitamins & Minerals DNA test analyses the genetic characteristics of metabolism for 23 nutrients: water-soluble vitamins (B1, B3, B5, B6, B9, B12, C), fat-soluble vitamins (A, D, E, K), macrominerals (calcium, magnesium, iron, phosphorus, sodium, potassium, iodine), and trace elements (zinc, selenium, copper, molybdenum, cobalt). The report describes the genetic characteristics of each nutrient from absorption to cellular use and provides genetic context for discussing the choice of supplement forms, dosages, and dietary strategies with a doctor.

The Genetic Profile: A Stable Layer of Information That a Blood Test Cannot Provide

A normal vitamin or mineral level in plasma and a normal level at the cellular level are two different things. Between them stands a system of transport proteins, enzymes, and receptors — one whose architecture is unique to each individual.

The Apixmed Prism genetic test provides an additional layer of information that standard assessments do not offer, and explains how the nutrient absorption system is structured. These data do not change over time and provide a stable context for more precise decisions regarding dietary adjustments and nutraceutical support.

Genetic test results are not a diagnosis and do not replace a consultation with a doctor. The Apixmed Prism report provides genetic context that complements clinical test results and supports informed decision-making together with your physician.

 

Sources

1. Vlieg-Boerstra, B., Bégin, P., Bruijnzeel-Koomen, C. A. F. M., et al. (2025). Vitamin Metabolism and Its Dependency on Genetic Variations Among Healthy Adults: A Systematic Review for Precision Nutrition Strategies. Nutrients, 17(2), 323.https://doi.org/10.3390/nu17020323

2. Usategui-Martín, R., De Luis-Román, D.-A., Fernández-Gómez, J. M., Ruiz-Mambrilla, M., & Pérez-Castrillón, J.-L. (2022). Vitamin D Receptor (VDR) Gene Polymorphisms Modify the Response to Vitamin D Supplementation: A Systematic Review and Meta-Analysis. Nutrients, 14(2), 360.https://doi.org/10.3390/nu14020360

3. Wójcik, M., Krawczyk, M., Wójcik, P., & Kieć-Wilk, B. (2024). MTHFR Gene Polymorphisms: A Single Gene with Wide-Ranging Clinical Implications — A Review. Genes, 16(4), 441.https://doi.org/10.3390/genes16040441

4. Mwangangi, D. M., van Ommen, B., & Verhoeven, A. (2022). Genetic Variations of Vitamin A-Absorption and Storage-Related Genes, and Their Potential Contribution to Vitamin A Deficiency Risks Among Different Ethnic Groups. Frontiers in Nutrition, 9, 861619.https://doi.org/10.3389/fnut.2022.861619

5. Huang, S., Ge, Y., Li, Y., Cui, N., Tan, L., Guo, S., Wang, S., Hao, L., Lei, G., & Yang, X. (2023). Magnesium Status, Genetic Variants of Magnesium-Related Ion Channel TRPM6 and the Risk of Gestational Diabetes Mellitus in Chinese Pregnant Women. Molecular Nutrition & Food Research, 67(22), e2200835.https://doi.org/10.1002/mnfr.202200835

6. Corrado, A., Rotondo, C., Cici, D., et al. (2025). Impact of Genetic Variants on Vitamin E Levels in an Italian Cohort of Bariatric Surgery Patients: A Focus on SNPs Involved with Transport and Bioavailability. International Journal of Molecular Sciences, 26(2), 651.https://doi.org/10.3390/ijms26020651

7. Wu, S., Yeung, A. M., Stafford, D. W., & Stafford, A. R. (2021). γ-Glutamyl Carboxylase Mutations Differentially Affect the Biological Function of Vitamin K-Dependent Proteins. Blood, 137(4), 533–543.https://doi.org/10.1182/blood.2020005526

8. Fedoniuk, L. Ya., Bilyk, Ya. O., Porokhovska, N. V., Matolinets, O. M., & Kulitska, M. I. (2026). Dynamics of the prevalence of thyroid gland diseases among the adult population. Wiadomości Lekarskie, 79(2), 425–432.https://doi.org/10.36740/WLek/218722

9. Khattar, V., Wang, L., & Peng, J.-B. (2022). Calcium selective channel TRPV6: Structure, function, and implications in health and disease. Gene, 817, 146192.https://pubmed.ncbi.nlm.nih.gov/35031425/

10. Olynyk, J. K., & Ramm, G. A. (2022). Hemochromatosis. New England Journal of Medicine, 387(22), 2053–2064.https://doi.org/10.1056/NEJMra2119758

11. Raina, R., Krishnappa, V., Das, A., et al. (2022). Overview of Monogenic or Mendelian Forms of Hypertension. Frontiers in Pediatrics, 7, 263.https://doi.org/10.3389/fped.2019.00263

12. Hennigar, S. R., Olson, C. I., Kelley, A. M., & McClung, J. P. (2022). Slc39a4 in the small intestine predicts zinc absorption and utilization: a comprehensive analysis of zinc transporter expression in response to diets of varied zinc content in young mice. Journal of Nutritional Biochemistry, 101, 108927.https://pubmed.ncbi.nlm.nih.gov/34843931/

13. Outzen, M., Tjønneland, A., Larsen, E. H., et al. (2018). Genetic polymorphism in selenoprotein P modifies the response to selenium-rich foods on blood levels of selenium and selenoprotein P in a randomized dietary intervention study in Danes. Genes & Nutrition, 13, 23.https://doi.org/10.1186/s12263-018-0608-4