Functional medicine testing: what it can tell you, and what it cannot
You have been told your bloods are normal and you still feel like this, so you start reading about functional medicine testing. By the end of the evening there are five panels open in browser tabs, all promising to explain you.
Functional medicine testing means privately ordered pathology tests that Medicare does not rebate: gut microbiome, hormones, DNA, IgG food panels, broad nutrient screens. They run in real laboratories, most cost between $300 and $800 in Australia, and no result on any of them is a diagnosis.
That last part is not me talking you out of testing. I order these tests most weeks and I think they earn their place. But I would rather you knew what you were buying, because what gets sold online is usually not the thing you actually receive.
The short version
- A functional test is an ordinary laboratory assay with an unusual menu. The lab is real. The reference range is the part that varies.
- In a randomised trial of 1,607 adults, personalised advice beat generic advice, and adding blood biomarkers and DNA on top of that advice added nothing measurable.
- People really do respond differently to the same meal. In PREDICT 1 the spread in glucose response between people was 68%. Genes explained very little of it.
- "Optimal range" is a marketing phrase as often as a clinical one. Check what units your result is in before you compare it to anything.
- The result is not the product. The reading is. A panel nobody interprets alongside the rest of your history is an expensive PDF.
What functional medicine testing actually is
Nothing mystical, and no separate class of laboratory.
It is a pathology test ordered outside the Medicare system, usually by a nutritionist, naturopath or integrative GP, usually on a menu of markers your GP would not routinely request. The specimen types are the ones you already know: blood, urine, saliva, stool, a cheek swab. Often the same accredited Australian labs your GP uses.
Three things make these tests different, and only the third is really about science.
The first is who can order them. Medicare pays for a defined list of tests for defined reasons, so anything outside that list is a private order and a private bill. It is also why the short list of tests you can order for yourself does not include most of them.
The second is the size of the menu. A GP panel asks a few specific questions. A functional panel asks dozens of them at once.
The third is the reference range, and that one deserves its own section further down.
The trial that asked whether the tests add anything
There is one large randomised trial that tested the actual promise, and it gets far less attention than it deserves.
Food4Me recruited 1,607 adults across seven European countries and split them four ways: generic dietary advice, or personalised advice built on their diet alone, or their diet plus blood biomarkers and body measurements, or their diet plus blood biomarkers plus five diet-responsive genetic variants. Six months. 1,269 people finished.
Personalised advice worked. Against the generic arm, people getting personalised advice ate less red meat, less salt and less saturated fat, took in more folate, and scored better on a healthy eating index.
Then the awkward part, in the researchers' own words: there was "no evidence that including phenotypic and phenotypic plus genotypic information enhanced the effectiveness of the PN advice."
A later analysis of the same trial went at it nutrient by nutrient, using the Australian Dietary Guidelines definition of discretionary foods, the ones high in fat, added sugars and salt. Fourteen outcomes. The comparison of "advice from your diet alone" against "advice that also used your blood tests and your DNA" returned p-values between 0.43 and 0.93. Not one of the fourteen came close to a difference.
Follow each line to the dotted vertical. That is the arm that got the blood biomarkers, and it has climbed back up towards the generic-advice arm. The trial does not test those two head to head, so read it as a picture rather than a p-value. It is still a picture worth sitting with before you spend $700.
To be fair to the tests, the paper does find something inside the personalised arms: the DNA arm beat the blood-biomarker arm on four of the fourteen measures. So this is not noise all the way down. It is that the comparison that matters to you, whether adding tests to good dietary advice makes the advice work better, came back with nothing.
What I take from Food4Me is not that tests are useless. It is that the personalising did the work, and most of the personalising came from somebody looking properly at what the person was already eating.
Where the variation genuinely is
The best argument for testing is that people really are different, and there is good evidence for it.
PREDICT 1 fed identical meals to 1,002 twins and unrelated adults in the UK and measured what happened next. The spread between people was enormous: a population coefficient of variation of 103% for blood triglyceride, 68% for glucose and 59% for insulin. Same food, completely different responses.
Which sounds like the case for a DNA test, until the next sentence. Genetic variants had "a modest impact on predictions": 9.5% for glucose, 0.8% for triglyceride, 0.2% for C-peptide. The gut microbiome carried more of it than the genes did.
Worth knowing who was behind it. Several of the authors consult to or work for a company selling personalised nutrition, and the paper says so. That does not make the numbers wrong, and I still think it is the best data we have on the question. It is the sort of thing I check before I quote a study, and I would rather tell you than not.
What I see in clinic. The pattern I meet most often is a woman in her forties who arrives with a gut microbiome report, a food intolerance report, and no ferritin result from the last two years.
Both reports are real and both are interesting. But we usually spend the first appointment on the ordinary bloods she has never had, and a good proportion of the time there is something in those that explains more of her week than either panel does.
She did not waste her money. She just bought chapter four first.
The five tests people ask me about
What each one measures, in plain terms, and the question it is genuinely able to answer.
| The test | What it actually measures | The question it can answer |
|---|---|---|
| Gut microbiome panel (stool) | The DNA of the bacteria present in one stool sample, on one day | Whether your microbial mix is unusual, and which fibres tend to feed what you have. It is not a test for gut disease, and bloating on its own rarely needs it |
| IgG food panel (blood) | IgG antibodies to food proteins. IgG rises with exposure, so foods you eat often tend to score high | Which foods might be worth removing and reintroducing in an ordered way, with someone watching. It is not an allergy test: allergy in Australia means skin prick or allergen-specific IgE, through a doctor |
| Hormone profile (dried urine or saliva) | Oestrogen, progesterone, testosterone, DHEA and the shape of cortisol across a day | Whether your cortisol pattern is flat or still raised at night, and how you are clearing oestrogen. Not a verdict on your hormones overall |
| DNA methylation panel (cheek swab) | Inherited sequence at variants in methylation-pathway genes. It reads sequence, and measures no methylation at all | Which nutrient needs are worth keeping an eye on across a lifetime, as context. Not an explanation for how you feel this month |
| Broad nutrient screen (blood and urine) | Vitamins, minerals, fatty acids and metabolic markers in one collection | Where the gaps are, so they can be confirmed and rechecked. This is the one that overlaps most with what your GP can already order, so it is worth checking what is on the Medicare list first |
If you want the longer version of any of these, we keep a guide to each test that explains the collection, the turnaround and what the report looks like.
"Optimal range" is a phrase worth being careful with
Reference ranges are one of the few places where a functional test really is doing something different, and it cuts both ways.
A pathology reference range is built from a population. It describes where most people sit. It was never designed to tell you what is right for you, which is the honest and genuinely useful half of the functional argument, and it is why "normal" can be perfectly true and still not explain your fatigue.
The other half is when a wider range gets quoted with more confidence than the narrow one it replaced.
Vitamin D is the clearest example and the one I correct most often. Australian labs report 25-hydroxyvitamin D in nanomoles per litre. American sources report it in nanograms per millilitre, and the two numbers differ by a factor of 2.5. Healthy Bones Australia recommends a level of at least 50 nmol/L year round, and puts mild to severe deficiency at over 30% of Australian adults.
So a vitamin D result of 40 is under the Australian target if it is in nmol/L, and double the Australian target if it is in ng/mL. Same number, same blood, opposite conclusion. Most of the "optimal range" advice you will read online is quoting the American unit without saying so.
Check which unit is on your report before you compare it to anything.
While we are here: Medicare does rebate a vitamin D test, item 66833, on a $30.05 fee. It rebates it for eleven specific reasons, among them signs of osteoporosis, malabsorption, deeply pigmented skin, and chronic and severe lack of sun exposure for cultural, medical, occupational or residential reasons. A lot of women meet one of those and have never been told.
The result is not the product
This is the thing I would most like you to take away, and it is the reason the trial evidence looks the way it does.
A 100-page report is not an answer. It is raw material. What turns it into something you can act on is somebody putting it next to your last two years of bloods, your cycle, your sleep, what you actually eat on a Tuesday, and the medicines and supplements you are already taking.
So the question to ask a practitioner is not "which test should I get". It is "what would you do with the result".
If the answer is a protocol they were always going to recommend, the test was decoration. If the answer changes depending on what comes back, the test is doing work.
I have written about this from the other direction too, as a way of filtering the noise. The right test depends entirely on the question you are trying to answer, and most people are handed the test before anybody has asked them the question.
Before you order anything, ask yourself
- What would I actually do differently once I had this result?
- Has anyone checked the ordinary things first: iron studies with ferritin, B12, folate, thyroid, vitamin D?
- Who is going to read this with me, and what do they sell?
- Is this test answering my question, or the question the website wanted to sell me?
- Am I buying the test, or the hope that something finally explains it?
That last one is not a criticism. It is the honest reason most people order a panel, mine included, and it is worth naming before the money leaves.
What to do this week, for nothing
The order matters more than the list.
- Find every blood test result from the last two years and put them in one folder. Most people have more data than they think, sitting in an email or a patient app.
- Book the GP and ask by name: full blood count, iron studies including ferritin, B12, folate, TSH, and vitamin D if you meet one of the item 66833 reasons. Ask for the numbers, not just "normal".
- Keep a two-week note. Energy on waking, energy at 3pm, sleep, and what you ate before each dip. Two weeks of that is often more useful than any panel, and it costs nothing.
- Then decide whether a functional panel adds anything, and make sure whoever reads it has seen the rest of the picture first.
If a nutrient keeps coming up in your reading, our micronutrient calculator will show you roughly where your food is putting you before you test for it.
Not sure which question you are actually asking?
That is the useful conversation, and it is free. Fifteen minutes on a call, no report, no kit. Tell me how you are actually feeling and how long it has been like that, and I will tell you honestly whether a test would add anything, including when the answer is that it would not.
Book a free 15-minute callNo obligation, and nothing is sold on the call.
Common questions
Is a functional medicine practitioner a real doctor?
Sometimes, often not, and the title is not protected in Australia. Some are GPs who have done extra training. Many are nutritionists, naturopaths or chiropractors. Ask what qualification the person holds, where they trained, and which professional association registers them. Nobody outside medicine can diagnose you, and nobody should be asking you to stop a prescribed medicine.
What is the difference between naturopath and functional medicine?
Naturopathy is a discipline with its own training and philosophy. Functional medicine is a framework that anyone can adopt, including GPs, dietitians, nutritionists and naturopaths. The difference you will actually notice is what the person orders and how they read it, not the label on the door. Ask about the qualification rather than the framework.
Where can I find functional testing in Australia?
Through a practitioner. Nutritionists, naturopaths and integrative GPs order these panels from Australian labs, and some are sold direct to the public online. The laboratory work is done here either way. What varies is who reads the result with you and whether they have seen the rest of your history, and that matters more than the lab does.
How much does a biomarker test cost?
In Australia most functional panels sit between about $300 and $800 for the test alone, with no Medicare rebate. A GP-ordered panel is usually bulk-billed or costs a small gap. Prices move, so check exactly what is included: the collection kit, the report, and whether anybody sits down and reads it with you afterwards.
Where can I get a blood test for vitamins and mineral deficiencies in Australia?
Start with your GP. A full blood count, iron studies including ferritin, B12 and folate are routinely rebated, and vitamin D is rebated under MBS item 66833 if you meet one of eleven listed reasons. A broader private nutrient screen through a practitioner is the next step if the ordinary bloods come back unrevealing.
What are the symptoms of mineral imbalance?
Vague ones, which is the whole problem: tiredness, poor concentration, cramps, low mood, hair changes, feeling the cold. Every one of those has a dozen other explanations, from low iron to a thyroid condition to broken sleep. Symptoms are the reason to test, never the result. They cannot tell you which mineral, or whether a mineral is involved at all.
Sources
- Celis-Morales C, et al. Effect of personalized nutrition on health-related behaviour change: evidence from the Food4Me European randomized controlled trial. International Journal of Epidemiology 2017;46(2):578-588. PMID 27524815.
- Livingstone KM, et al. Personalised nutrition advice reduces intake of discretionary foods and beverages: findings from the Food4Me randomised controlled trial. International Journal of Behavioral Nutrition and Physical Activity 2021;18:70. PMID 34092234.
- Berry SE, et al. Human postprandial responses to food and potential for precision nutrition. Nature Medicine 2020;26(6):964-973. PMID 32528151.
- Healthy Bones Australia. Vitamin D and bone health.
- Australian Government Department of Health. Medicare Benefits Schedule item 66833.
- Australasian Society of Clinical Immunology and Allergy. Allergy testing.
- Healthdirect Australia. Vitamin D deficiency.
Important: This article is general information written by a clinical nutritionist. It is not medical advice and does not replace care from your GP or another qualified health professional. Functional testing does not diagnose, treat, cure or prevent any condition, and results are best interpreted alongside your symptoms, history, medications and supplements.
Written and reviewed by Georgina Waugh
Clinical Nutritionist, BHSc Nutritional Medicine
Last updated: 15 June 2026
Sources reviewed: Food4Me (2017 and 2021), PREDICT 1 (2020), Healthy Bones Australia, the Medicare Benefits Schedule, ASCIA and Healthdirect.