The tests I sometimes use in clinic - and why they’re not always the first step
Thoughts on functional testing, clinical judgement, cost, context and why testing tools should always serve the person, not the other way around...
Introduction
One of the things I’m very open about in my work is this: I don’t always use testing and do not need it to work with any client, but when I do, it’s for a clear reason.
Functional testing can be incredibly helpful, but it’s not something I apply automatically or routinely at the beginning of every client journey. My role as a nutritionist isn’t to order tests. It’s to understand patterns, context and presentation and decide when testing will genuinely add clarity.
I’ve also completed tests I use in clinic on myself. I think it’s important to understand not just the results, but the process, cost and experience from the client’s point of view and how results actually translate into real life changes.
When I use testing and when I don’t
Sometimes, we can make excellent progress without any testing at all.
A thorough case history, symptom timeline, dietary assessment and lifestyle review often provide more than enough information to begin effective work, particularly in the early stages. In fact, testing is sometimes more useful later, once foundations such as digestion, blood sugar balance, stress support and basic nutrition are in place.
Before suggesting a test, I ask:
Will this test meaningfully change what we do?
Do we need this information now?
Could we work clinically first and reassess?
Is this an affordable option for my client or not?
Testing is a tool, not a requirement.
Evidence and healthy scepticism
Functional testing does attract some criticism and some of that is understandable.
Not all tests have strong large scale studies behind them for various reasons and results don’t always fit neatly into conventional diagnostic frameworks. There are also valid concerns around over testing, over supplementation and interpretation without adequate training. Many functional tests have good analytical validity but more limited clinical outcome evidence, largely because current research models aren’t well suited to complex, individualised tools.
I shared many of these concerns myself early on. I was a little sceptical at first.
What changed my view wasn’t trends or marketing, but experience. Seeing how they work in the labs and the rigorous processes involved. Seeing patterns repeat across different clients. Using tests selectively rather than routinely. Comparing results with symptoms and progress and making sure not to forget the person at the centre of it all. Completing the tests myself and understanding both their strengths and limitations.
These tests are not diagnostic tools. They are functional and interpretive. When used poorly, criticism is justified. When used carefully, they can offer insight that standard testing sometimes misses.
The question for me is never whether a test is perfect, but whether it helps us make better, safer and more personalised decisions.
Stool testing - when gut information is needed
When gut symptoms are ongoing, complex, or not responding as expected, stool testing can be extremely informative.
I sometimes use comprehensive panels from labs such as Genova Diagnostics and Microba.
These can provide insight into digestive capacity, microbiome balance, yeast, parasites and pathogenic bacteria, gut inflammation and immune markers and intestinal barrier integrity.
These are advanced clinical tools, not screening tests. They’re not always appropriate at the start, and they’re not always necessary.
Sometimes I also begin with simpler and more accessible markers, which can give valuable information without the cost or complexity of full panels.
Hormone testing - used strategically, not routinely
Hormone testing can be very helpful, when used at the right time.
I sometimes use the DUTCH Test or HUMAP to explore sex hormone patterns, cortisol rhythm, adrenal support and hormone detoxification pathways.
That said, hormone testing is not always the first step. Many hormone related symptoms improve once we address blood sugar balance, gut health, stress load and nutrient sufficiency.
Testing later, once the system is more stable can sometimes give more clinically useful results.
Metabolic and nutrient pathways
One test I sometimes use and have completed myself is the Metabolomix+ via Genova.
This looks at organic acids, amino acids, fatty acid metabolism, B vitamin and antioxidant needs, mitochondrial function and detox pathways.
It can be very insightful, particularly when symptoms are complex or long standing. It’s very detailed and looks deeply at what your body is actually doing with the nutrients you’re eating - how they are processed, but it’s also nuanced and needs good analysis of all the results together to give an overall picture. I most often collaborate with the lab after this test to get extra insight on this to double check my own analysis of what’s going on!
It also can contain add ons like omega ratio and a few key genetic variants that can be helpful to consider, depending what clients present with initially, such as whether the body may process folate and B vitamins in a different way, or need more or less of certain types of nutrients. It’s fascinating but did it ever scare the living daylights out of me when I did my first one, trying to read through it all - I’ve got used to it now, thankfully!
Genetic testing insight
I’m currently studying with Lifecode GX to explore genetic tendencies further, as I’ve found it really useful personally and also with clients, and have become quite geeky about it!
Completing this test myself gave me valuable insight into my own health. Learning that I have slow COMT activity for example helped explain patterns around stress sensitivity and why certain approaches feel supportive for me, while others don’t. (COMT stands for Catechol-O-Methyltransferase - it’s an enzyme that’s needed for breaking down certain neurotransmitters such as dopamine, as well as oestrogen).
Genetics don’t tell us what will definitively happen to us though - they are not a crystal ball. They just offer additional context around what may need support. They’re never used in isolation and they’re never essential for progress, but they can help refine decisions around food, lifestyle and supplements and I’m really excited to see how this progresses in the future in general and my own practice.
Cancer support and testing considerations
Now that I am cancer trained, certain tests may be used selectively at specific points in a client’s journey.
This might include monitoring inflammation or immune markers, assessing digestive or absorptive capacity, or supporting nutritional status during or after medical treatment.
As always, testing is used alongside clinical judgement and within scope, not routinely or indiscriminately.
How testing can guide food and supplement choices
When testing is used appropriately, it can help decide whether supplements are needed at all, guide the right type, dose and timing, and highlight foods that may be particularly supportive or potentially more problematic.
Equally, when testing isn’t used, these decisions are still guided by symptoms, history and response to change. Testing can help refine a plan, but it never replaces the basics of good clinical nutrition and lifestyle support.
Why some tests aren’t widely available
Many of the tests I use aren’t available directly to the public and there’s a reason for that.
They require clinical context, skilled interpretation and individualised application. Without that, results can be confusing or misleading.
My role isn’t simply to access tests. It’s to make sense of them.
Cost matters and how we work around it
Testing can be expensive, which is why we don’t test unless it’s likely to add value.
We often work very successfully without testing. Smaller targeted markers are used where appropriate. Some labs, including Genova, offer payment plans. Testing can also be phased over time rather than done all at once. Sometimes all that’s needed is a quick vitamin D test to get going.
Good support never depends on someone’s ability to afford tests.
Using GP testing where appropriate
Where appropriate, I will often guide clients on which standard GP or NHS tests may be helpful to request and how to ask for them clearly, often communicating with them myself.
This might include vitamin D, iron markers, thyroid tests or inflammatory markers. These tests are often free, but they’re not always offered without a clear rationale.
I can’t guarantee tests on your behalf and I don’t replace your GPs advice, but I can help you understand which markers may be relevant, how to frame your symptoms and how to use existing results more effectively.
Sometimes these standard tests give us all the information we need, for free (except for the paying taxes bit!).
Final thoughts
Functional testing isn’t perfect and it shouldn’t be treated as definitive.
Used thoughtfully, it can offer clarity. Used indiscriminately, it deserves criticism.
I started out sceptical. Experience, self testing and careful application have shown me where these tools are genuinely useful and where they’re not.
Sometimes the most effective work happens without a single test. Other times, the right test at the right moment can make a difference.
Knowing the difference is part of my job.
Want to work together?
If you’re unsure whether testing is right for you, or you have results that don’t quite make sense, or ongoing symptoms when your blood tests tell you everything is ‘normal’, this is exactly where I can help.
We can work effectively without testing, use existing GP or private results more confidently, decide if and when testing might add value and build a plan that fits both your health needs and your budget.
You don’t need to arrive with tests and you don’t need to commit to them either.
If you’d like personalised support, you can explore working with me or get in touch to discuss your next steps.
Clarity first. Testing only when it truly helps…