Persistent fatigue is one of the most common reasons patients book a functional medicine consult - and one of the most under-investigated symptoms in conventional care. A normal CBC and a TSH inside the lab range do not rule out a real, fixable problem. They rule out roughly five problems out of dozens.
The five drivers we see most often
- Suboptimal thyroid function (free T3, reverse T3, and antibodies - not just TSH).
- Iron and ferritin in the lower quartile, even when 'normal.'
- Cortisol dysregulation from chronic stress, poor sleep, or post-viral inflammation.
- Nutrient depletion - B12, vitamin D, magnesium, and zinc are common.
- Hidden infections, including chronic Lyme and tick-borne co-infections.
Why standard labs miss it
Conventional reference ranges are statistical descriptions of a sick population, not definitions of optimal function. A ferritin of 18 is 'normal' on most lab reports, but it's a near-certain driver of fatigue in a 35-year-old woman. Functional medicine uses tighter, evidence-based optimal ranges and looks at patterns across panels - not isolated red flags.
When to ask for a different approach
If you've been told 'everything looks fine' more than once, but you don't feel fine - that's the moment to escalate, not to accept it. Bring your prior labs to a free 30-minute consultation call. We'll tell you honestly whether there's more to investigate or whether a different specialist is the right next step.
