The complete Test, Don't Guess series — clinical investigation, practitioner reality, and the body you are living in. Books One to Three are available on Amazon; Metabolic Natures is being rewritten.
The Test, Don't Guess series grew out of nearly forty years of working with people — and from a single observation that has never changed: the gap between what standard investigation finds and what is actually happening is where most chronic health problems live.
The four books address that gap from four different angles. Together they form a complete clinical philosophy. Each stands alone. Metabolic Natures — Book 4 — is being rewritten and is not on sale at present.
The foundational book. Why standard testing is designed to miss functional dysfunction. What five tests — blood chemistry, GI-MAP, DUTCH Plus, Organic Acids, and food sensitivity — reveal that a standard panel cannot. How to read results to optimal rather than just normal ranges. The framework that connects findings into a protocol.
"Your tests are normal. But normal is not the same as optimal — and the distance between those two points is where most chronic health problems live."
The test results are not the hard part. Getting someone to act on them — consistently, sustainably, in the actual Tuesday morning of their life — that is the hard part. And nobody puts it in the course materials. The psychology of behaviour change, the neuroscience of recovery, the conversations that determine whether a protocol works. The human layer of functional medicine.
"The test results are not the hard part. Getting someone to act on them — consistently, sustainably, in the actual Tuesday morning of their life — that is the hard part. And nobody puts it in the course materials."
Your body is not seven separate problems waiting for seven separate specialists. It is one interconnected system — and the fatigue, the hormonal disruption, the weight that won't shift, the gut symptoms that persist despite the perfect diet — these are not mysterious. They are the predictable downstream consequences of upstream disruptions that standard investigation doesn't look for. This book looks for them.
"Your body is not seven separate problems waiting for seven separate specialists. It is one interconnected system — and its disruptions are predictable, not mysterious, once you know where to look."
Two axes. Six positions. A place to start — being rewritten to the current method
Why does every diet work for someone and fail someone else? People really do respond differently to the same food. Metabolic Natures is a framework for deciding where to start: six positions on two axes, read from a questionnaire and adjusted by what testing shows about how the body is working now.
No test confirms a position — the tests describe current function, not type — and the earlier edition said otherwise in places. It is no longer on sale while it is rewritten. The dated correction lists what changed.
"The question was never which diet is correct. The question was always which metabolic system it was operating on — and whether those two things were compatible."
The Starter Edition of Test, Don't Guess is currently in production as an audiobook — narrated by Stephen Duncan using a professional voice clone. 20 chapters, 23,000 words. For the commute, the walk, the gym. Available on major platforms when released.
If you have NHS blood results, private lab results, or have already run a GI-MAP, DUTCH Plus, or OAT — the Detective Health interpretation guides give you the clinical framework to read them properly. Each guide covers one test in depth: optimal rather than normal reference ranges, what the markers mean, and how to connect findings to symptoms. Available at detective-health.com/products. If you want to run a test from scratch, ask on the free 20-minute call.
See the Interpretation Guides →The TDG Five-Test Programme is the clinical investigation the books describe — applied to you, your results, your biology.