Your check-up came back fine. Blood sugar, blood lipids, liver, kidneys – all within the reference range. And yet you wake up tired, your gut is often unsettled, after stressful weeks you barely recover, and you catch infections more often than you used to. Does that add up?
Yes. Standard blood tests mainly answer one question: is a common disease present? They say little about how your gut works, how your stress axis regulates over the day, how well your cells cope with strain, or which nutrients actually arrive. This is where functional laboratory diagnostics comes in.
At a glance
- What it's about: Your check-up is fine, yet you are tired, your gut is unsettled and recovery is hard. Standard values mainly show whether common diseases are present – not how systems work.
- Possible causes: disturbed digestion and gut barrier, a cortisol curve out of rhythm, oxidative stress with depleted glutathione and low nutrient levels in cells – often connected.
- What you can do: use statutory screening, clarify your question and measure specifically; with acute or severe symptoms see a doctor immediately.
- What can be measured: microbiome, gut barrier and absorption in stool, cortisol daily profile in saliva, cell stress and metals in urine, minerals in whole blood, amino acids and fatty acids in capillary blood.
Why good standard values don't tell the whole story
A serum value is a snapshot of what is circulating in the blood at that moment. It does not show how an organ works or how a regulatory loop swings over the day. Many changes begin quietly: in the gut lining, in the rhythm of the stress hormone cortisol, in the balance between free radicals and the cell's protective systems. They can persist for a long time before they show up in a standard value.
The screening offered by statutory health insurance remains important – you should use check-ups and cancer screening. Functional diagnostics asks a different question: how do the systems work together? To answer it, it measures where these processes become visible – in stool, urine, saliva and whole blood. Which individual values are often missing from a standard blood count is covered in Always tired, but your blood tests are fine?.
1. Gut and digestion: what isn't absorbed doesn't arrive
Even the best diet is of little use if digestion and absorption don't work. Nutrients are broken down in the gut and taken up into the blood through the intestinal lining. The lining is both filter and protective barrier: it lets nutrients pass and holds back bacterial components and undigested substances. A disturbed barrier is now considered one factor in various inflammatory and metabolic diseases (PubMed 28650209) (PubMed 40086468).
The microbiome – the community of gut bacteria – is part of this: it breaks down fibre, produces short-chain fatty acids that feed the gut cells, makes vitamins and influences metabolism and the immune system (PubMed 35105664). And a large part of the immune system sits in the lymphatic tissue of the gut wall (PubMed 33753873).
Measurable markers include the composition of the microbiome, gut barrier markers such as zonulin, inflammation markers such as calprotectin, indicators of digestive capacity, histamine, and small intestinal bacterial overgrowth via a breath test. Suitable analyses: Gut barrier & absorption, Gut profile microbiome & gut barrier, Microbiome Maxi Plus, Gut health & digestion check-up, SIBO breath test and Histamine & DAO analysis. More: Nutrients not being absorbed?
2. Cell stress and antioxidant defence: how well does the cell protect itself?
Every cell constantly produces reactive oxygen species – a normal by-product of energy production, increased by strains such as smoking, environmental substances, inflammation or intense long-term stress. The body counters them with protective systems. When the balance tips, this is called oxidative stress (PubMed 28819546).
The most important protective molecule inside the cell is glutathione. It neutralises free radicals, regenerates other antioxidants and is involved in processing many substances. The body makes it from the amino acids cysteine, glycine and glutamate; the enzymes that work with glutathione need selenium, among other things (PubMed 14988435) (PubMed 37683986). If this defence cannot keep up with the strain, damage to cell components and DNA results. A well-studied marker of this is 8-OHdG, which can be measured in urine (PubMed 19412858). Metals such as lead, cadmium or mercury can also increase oxidative stress (PubMed 21414382).
Suitable analyses: Cell stress profile (oxidative and nitrosative stress), 8-OHdG test, Nitrosative stress test, Heavy metal urine test and Organic acids in urine as a mirror of cell metabolism and mitochondria. The building blocks of glutathione are shown by Prevent 360 (amino acids) and the whole blood mineral analysis (including selenium and zinc).
3. The silent stress axis: when cortisol loses its rhythm
Cortisol follows a clear daily rhythm: it rises steeply shortly after waking, falls over the day and is lowest at night (PubMed 26563991). This rhythm helps determine when you are alert and productive and when you recover.
Cortisol raises blood sugar – that is its job in acute stress. If it stays elevated, this is associated with insulin resistance, more abdominal fat and higher blood pressure; experts discuss cortisol as one driver of metabolic syndrome (PubMed 19470627) (PubMed 31713487). The daily curve matters too: in a large study of British civil servants, a flatter cortisol curve was associated with higher cardiovascular mortality (PubMed 21346074), and a meta-analysis found flatter slopes across a range of physical and mental health problems (PubMed 28578301).
A single morning blood value says little about this rhythm. A daily profile in saliva covering several time points is more informative (PubMed 19095358). Suitable analyses: Cortisol daily profile with DHEA, Stress & sleep lab package and Neurotransmitter Plus. More on the link with sleep: Cortisol and melatonin.
4. Nutrients: what reaches the cell
Many minerals are mainly found inside cells, not in serum. For magnesium, only about one per cent is outside the cells, so a normal serum value does not rule out low stores (PubMed 30513803). A whole blood analysis includes the blood cells. Amino acids are the building blocks for enzymes, messengers and glutathione; fatty acids form cell membranes.
Suitable analyses: Prevent 360 (amino acids, fatty acids, nutrients), Whole blood mineral analysis (magnesium, zinc, selenium), Vitamin check basic (B12, folic acid, D, E, Q10) and the Omega-3 test.
How the four areas are connected
None of these areas works alone. The gut helps decide which nutrients arrive – including the building blocks of glutathione. Long-term stress changes digestion, sleep and blood sugar. Cell stress uses up protective substances that have to be replenished through food. That is why it pays to look not just at one value but at how they interact.
| Your question | Area | Sample |
|---|---|---|
| Unsettled digestion, bloating, nutrients not arriving? | Gut and absorption | Stool, breath |
| Environmental and metal exposure, cell protection? | Cell stress and antioxidant defence | Urine |
| Exhausted, poor recovery, disturbed sleep? | Stress axis | Saliva, urine |
| How well supplied am I? | Nutrients | Capillary blood, whole blood |
The limits – stated honestly
Functional values are snapshots too. They vary with time of day, diet, sleep and strain. Reference ranges apply to groups, not to the individual. An abnormal value is not yet a disease, and a normal one is no guarantee. Not every analysis makes sense for every question – so a good choice starts with the question you want to answer.
How to go about it
- Use statutory screening: check-ups and cancer screening remain the basis.
- Clarify your question: is it about digestion, exhaustion, exposure or supply?
- Measure specifically: one analysis that fits this question – not everything at once.
- Watch the trend: repeating after a few months shows whether anything is changing.
- Discuss the results: the ORY expert team or your doctor can help you interpret them.
With acute or severe symptoms – such as chest pain, shortness of breath, blood in the stool, marked unintended weight loss or high fever – don't wait for a test; see a doctor immediately.
Frequently asked questions
What is the difference between a standard blood test and functional diagnostics?
A standard blood test mainly checks serum values that point to common diseases. Functional diagnostics measures how systems work – such as the gut barrier and microbiome, the cortisol curve over the day, markers of cell stress or minerals in whole blood.
Why stool, urine and saliva instead of just blood?
Because some processes become visible there: gut markers in stool, breakdown products of cell damage in urine, the free fraction of cortisol in saliva at several points of the day.
How do I prepare for a home test?
Every kit includes instructions. What matters most is the right timing of the sample and notes on diet or medication. Do not stop prescribed medication without consulting your doctor.
How long does it take to get results?
That depends on the analysis. Processing starts when the sample arrives at the laboratory; the time is stated on each product page.
Does health insurance cover the cost?
Usually not. Functional laboratory analyses are mostly self-pay services. Private insurers sometimes reimburse – ask them beforehand.
Who explains my results?
You receive the report with the laboratory's reference ranges. For interpretation you can book a session with the ORY expert team or discuss the report with your doctor.
Important note: This article does not replace medical advice, diagnosis or treatment. It is for general information only. Laboratory values alone do not make a diagnosis. If symptoms persist or are severe, please consult your doctor.
Sources
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- Neurath MF et al. The intestinal barrier: a pivotal role in health, inflammation, and cancer. Lancet Gastroenterol Hepatol. 2025. PubMed 40086468
- de Vos WM et al. Gut microbiome and health: mechanistic insights. Gut. 2022. PubMed 35105664
- Mörbe UM et al. Human gut-associated lymphoid tissues (GALT); diversity, structure, and function. Mucosal Immunol. 2021. PubMed 33753873
- Pizzino G et al. Oxidative Stress: Harms and Benefits for Human Health. Oxid Med Cell Longev. 2017. PubMed 28819546
- Wu G et al. Glutathione metabolism and its implications for health. J Nutr. 2004. PubMed 14988435
- Lapenna D. Glutathione and glutathione-dependent enzymes: From biochemistry to gerontology and successful aging. Ageing Res Rev. 2023. PubMed 37683986
- Valavanidis A et al. 8-hydroxy-2'-deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis. J Environ Sci Health C. 2009. PubMed 19412858
- Jomova K, Valko M. Advances in metal-induced oxidative stress and human disease. Toxicology. 2011. PubMed 21414382
- Stalder T et al. Assessment of the cortisol awakening response: Expert consensus guidelines. Psychoneuroendocrinology. 2016. PubMed 26563991
- Anagnostis P et al. The pathogenetic role of cortisol in the metabolic syndrome: a hypothesis. J Clin Endocrinol Metab. 2009. PubMed 19470627
- Sharma VK, Singh TG. Chronic Stress and Diabetes Mellitus: Interwoven Pathologies. Curr Diabetes Rev. 2020. PubMed 31713487
- Kumari M et al. Association of diurnal patterns in salivary cortisol with all-cause and cardiovascular mortality: findings from the Whitehall II study. J Clin Endocrinol Metab. 2011. PubMed 21346074
- Adam EK et al. Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis. Psychoneuroendocrinology. 2017. PubMed 28578301
- Hellhammer DH et al. Salivary cortisol as a biomarker in stress research. Psychoneuroendocrinology. 2009. PubMed 19095358
- Razzaque MS. Magnesium: Are We Consuming Enough? Nutrients. 2018. PubMed 30513803
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