I'm not going to tell you that ADHD isn't real, that stimulant medication doesn't work, or that you just need to eat more vegetables. ADHD is real. Stimulant medication helps many people significantly. And the system that's asking you to wait 2–3 years for an assessment while your work, relationships, and mental health deteriorate is genuinely failing you.
What I am going to tell you is that the current pathway — assessment, diagnosis, prescription — misses something important. Something measurable. Something that, in my clinical experience, is present in almost every adult who comes to me with significant ADHD-type symptoms, whether diagnosed or not.
The missing piece is this: nobody investigates why the brain isn't working the way it should.
The question that almost never gets asked
The current ADHD assessment pathway is built around behavioural observation. You complete questionnaires. A clinician interviews you about your symptoms across multiple life domains. Your history is reviewed. A diagnostic decision is made based on whether your symptom pattern matches the DSM criteria. If it does, you receive a diagnosis. If the diagnosis is ADHD, you receive a prescription for stimulant medication.
That's the pathway. At no point in that pathway does anyone ask: why is your dopamine system underperforming? What in your biochemistry is producing this symptom pattern? Is there something measurable and addressable driving the neurotransmitter deficits that stimulant medication is compensating for?
This matters because stimulant medication — methylphenidate, lisdexamfetamine, atomoxetine — works by increasing dopamine and norepinephrine availability in the prefrontal cortex. It addresses the downstream deficit. It doesn't address why the deficit exists. For many people that's sufficient. For a significant proportion, medication provides partial relief, loses effectiveness over time, or creates problems that complicate the picture. When that happens, the biochemical investigation becomes essential.
The four biochemical root cause clusters
Through clinical practice and five-test functional investigation, I've identified four consistent biochemical patterns that underlie or contribute to ADHD-type presentations. These aren't alternative diagnoses — they're measurable physiological states that can coexist with a genuine ADHD diagnosis and compound it significantly.
Why the waiting period is actually the right time
If you're on a 2-year NHS waiting list, or you've just been assessed privately and have a diagnosis but medication that isn't working as well as you'd like, you have two years in which you can either wait passively or investigate actively. The biochemical investigation doesn't require an ADHD diagnosis to be clinically meaningful. The findings — low ferritin, poor methylation, gut dysbiosis, blood glucose instability — are relevant regardless of diagnostic status, and the interventions produce real changes in how the brain functions.
I've seen clients whose ADHD symptoms improved meaningfully within 8–12 weeks of addressing ferritin deficiency, blood glucose stabilisation, and gut restoration — before they'd reached the top of any waiting list. That's not a cure for ADHD. But it's the difference between a brain trying to function on depleted resources and a brain with the biochemical foundation it needs to use whatever tools — medication, coaching, strategies — are brought to bear.
A client in her mid-thirties came to me while on an 18-month NHS waiting list. She'd been managing significant attentional and executive function difficulties her whole adult life — jobs lost, relationships strained, an exhausting sense of being fundamentally broken in some way she couldn't name. Standard bloods: normal. GP's response: stress management and therapy.
Testing revealed ferritin of 11 (impaired dopamine transport), fasting insulin consistent with early insulin resistance affecting prefrontal cortex function, significant gut dysbiosis with low secretory IgA, and on OAT, substantially low HVA — direct evidence of impaired dopamine production. We addressed each in sequence. Within three months she described her mind as "quieter than it's been in years." She subsequently received her ADHD diagnosis and started medication, which she found significantly more effective on the corrected biochemical foundation than she expected to based on others' experiences.
What functional medicine can and cannot do
To be direct: functional medicine doesn't diagnose ADHD. I'm not an ADHD assessor and the TDG programme isn't a substitute for a proper diagnostic assessment. What it does is investigate the biochemistry that may be driving, compounding, or in some cases mimicking ADHD symptoms — and address whatever measurable deficits are found.
Some of my clients find that addressing these deficits resolves symptoms sufficiently that they choose not to pursue diagnosis or medication. Others find that it makes their diagnosis, when it arrives, easier to work with — because they're not fighting both ADHD and a depleted biochemical foundation simultaneously. Neither outcome can be predicted in advance. What can be established in advance is whether the biochemical patterns are present — and that takes five tests and about four weeks.
A free starting point
The Neurodivergent Biochemical Screen is a free 18-question tool that identifies which of the four biochemical clusters is most likely active in your presentation. It doesn't diagnose anything. It provides a clinical orientation — a starting point that identifies where investigation is most likely to be productive, and which of the five TDG tests are most relevant to your specific pattern.