The physical side of mental health: what blood and gut testing can reveal

Mental health is complex. Genetics, life events, relationships, money worries and sleep all play a part, and none of that is undone by a lab result. But there is a second, quieter part of the picture that often gets missed: the body. Your gut, your hormones and a few key nutrients all talk to your brain, and when one of them is off, it can look and feel a lot like a mental health problem, or make an existing one harder to shift.

This matters because these physical factors are testable, and many of them are treatable. A person who is exhausted and flat because their iron stores are empty needs iron, not just encouragement. Someone whose thyroid has quietly slowed down can spend months being treated for depression when the root cause is sitting in a blood tube. None of this replaces mental health care. It sits alongside it, and it can stop you guessing.

Your gut and your brain are on the same line

The gut and the brain are wired together. They communicate constantly through nerves, hormones and the immune system, a network scientists call the gut-brain axis. The vagus nerve is the main cable running between them, and the trillions of microbes living in your gut are active participants in the conversation, not bystanders.

According to a 2025 review in Cellular & Molecular Immunology, this gut-immune-brain axis is a genuinely two-way system: gut microbes and the substances they produce influence immune signalling and brain function, and disruption of the gut microbiome and the gut barrier has been implicated in depression and anxiety, among other conditions. [DOI] Much of the detailed mechanism still comes from laboratory models, so this is an emerging field rather than a settled one, but the direction of travel is clear. A separate 2024 review in Neuroscience & Biobehavioral Reviews describes how an imbalanced gut microbiome, or dysbiosis, can disturb this gut-brain communication and contribute to neuropsychological difficulties. [DOI]

There is a local dimension too. South African gut microbiomes differ from the populations most gut research has been built on. The 2025 Nature study expanding the human gut microbiome atlas of Africa found that geography is one of the strongest influences on gut composition, and that urban, lower-fibre diets are associated with the loss of helpful fibre-fermenting microbes. Our own head of laboratory, Prof Veron Ramsuran, is a published authority on the South African gut microbiome, so this is not distant science for us.

What your blood can say about your mood and energy

Several routine blood markers have a well-documented relationship with mood, concentration and energy. When one of these is low or out of range, the effects can be mistaken for a purely psychological problem. Here is what the research says about the most useful ones.

The theme across all of these is the same: they are common, they are easy to measure, and they are fixable. Reading them off your symptoms is impossible, because low iron, low B12, a slow thyroid and low vitamin D can all produce the same tired, flat, foggy feeling. A blood test tells them apart.

Why this matters in South Africa

South Africa carries a heavy mental health load and a wide treatment gap. Access looks very different depending on where you sit. In the private space, the barrier is often awareness and time rather than money. In under-resourced communities, the nearest psychiatric facility can be many kilometres away and the cost of a single consultation is out of reach. Economic pressure, unemployment, load-shedding, crime and the long tail of the pandemic all add to the strain.

The physical contributors described above are also common here. Iron deficiency is one of the most widespread nutritional problems in the country, especially among women of reproductive age. Vitamin D deficiency is more common than our climate suggests. For visitors and newer arrivals, a change in diet, sunlight and routine can shift these markers within months. Checking them is a low-cost, practical first step that does not depend on a scarce specialist appointment, and it can be done the same way whether you are paying privately or watching every rand.

Testing is a starting point, not a diagnosis

It is worth being clear about what testing can and cannot do. A blood or gut test cannot tell you that you have depression or an anxiety disorder, and a normal set of results does not mean your distress is imaginary. What testing does is rule physical contributors in or out, so that a low mood driven by an empty iron tank or a sluggish thyroid gets the right treatment, and so that mental health support is not working against a hidden headwind.

If you are struggling, the most important step is to reach out to a professional or someone you trust. Talking therapy and, where appropriate, medication prescribed by a doctor are the mainstays of care, and they work. Testing is a useful companion to that, not a substitute for it.

What you can test at Epicentre, and where to start

You do not need a doctor's referral, and you do not need to see a specialist first. You can walk in at any Epicentre branch in Cape Town, Durban or Johannesburg, or order online. Here is the useful part: all six of the mood-linked blood markers in this article, iron and ferritin, vitamin B12, vitamin D, thyroid, inflammation and blood sugar, sit together in our Mental Health Wellness Analysis, alongside stress markers like cortisol, magnesium and homocysteine, so you do not have to piece them together yourself.

Prefer a single targeted test? Iron and ferritin sit in the Iron & Anaemia Panel, and thyroid has its own Thyroid Panel. If you would rather a broader annual picture, the ODx Max panel goes wider still. Every blood test comes with a plain-language ODx functional health report that colour-codes your markers against optimal ranges, not just the wide normal ranges, so a level that is drifting shows up early. If you would rather understand your numbers first, our guide to understanding your results explains every marker in plain language.

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Medically reviewed by Dr Samantha Naidoo, MB ChB, FCP (SA), Medical Director at Epicentre. This article is for general education and does not replace personal medical or mental health advice. If your symptoms are affecting your daily life, please speak to a healthcare professional.