PSA: "normal" bloodwork is "average" bloodwork

And the average American is not exactly thriving.

Picture the scene: you are a young, never smoker, with a normal BMI. Your doctor isn’t worried about you. You aren’t a hypochondriac, but you are concerned something is “off.” You are juggling kids and responsibilities and running on fumes. You go to your annual physical and get some standard bloodwork done, and it’s all either “normal,” or “nothing to worry about.” You’re sent on your way with an eye roll or a gold star, feeling crazy, difficult, or alone.

For years, this was me. “Perfect” labs while feeling like everything was off, and a baseball-sized tumor quietly growing in my neck. When I finally discovered my thyroid tumor, I became obsessed with two questions: how do I get rid of this thing, and how did I get it in the first place? (Since I wasn’t, you know, exposed to Chernobyl.) How could I be an “A student” at every physical with “normal” bloodwork while harboring a 6cm mass in my neck?

The second question led me to get expanded bloodwork through Function and to work with a functional medicine doctor who taught me something that should be obvious but somehow isn’t: there’s a massive difference between “normal” lab results and lab results that indicate you’re actually thriving. “Functional” results, as they say.

I learned that most reference ranges on your lab results are based on the average values of the population being tested, which, in the US, often means metabolically struggling, chronically inflamed, and far from optimal. These ranges tell you if you’re in the same ballpark as everyone else. They often fail to adjust for age, sex, genetics, menstrual phase, personal baselines, or health goals (like optimizing fertility). This means there’s a big difference between bloodwork that is normal and bloodwork that is optimal. I don’t know about you, but this was a major lightbulb moment for me.

How did this happen? Most lab reference ranges calculate the central 95% of their values. That becomes the “normal range.” It’s also practical for labs and clinicians to use a consistent, population-based range, which creates a shared language across providers. Of course, most clinicians would say this is why you should never look at test results in a vacuum, and all other health information, symptoms, family history, etc must get taken into account by a doctor. But in reality, many of us get only a few minutes of review, and lab results often carry outsized weight in those conversations, especially if they’re stamped as “normal.” There isn’t the time (or the culture) to do deeper investigations.

Optimal or “functional” ranges are drawn from clinical literature, expert consensus, and patient-reported outcomes, and reflect where people tend to feel their best, not just avoid disease. They aren’t perfect, and the field isn’t without debate. But for me, they were a starting point that helped explain where my body was struggling, and what I could do to support myself better.

Here are some examples I learned, though can vary based on the lab:

• TSH (thyroid stimulating hormone, a key signal for thyroid function)

  • Reference range: 0.4 – 4.5 mIU/L

  • Optimal range: ~1.0 – 2.5 mIU/L for most

  • Why it matters: You can be at 4.0 and be technically normal, even though at 2.0 many people starting getting hypothyroid symptoms like bone-deep exhaustion, brain fog, hair thinning, weight gain, or the reason why you are always so.damn.cold.

• Vitamin D

  • Reference range: 30 – 100 ng/mL

  • Optimal range: 50 – 80 ng/mL

  • Why it matters: 31 is technically “fine” but is associated with higher risk of infections, fatigue, and mood instability. The seasonal depression that hits harder each winter, especially when you’re stuck indoors with kids. The way you catch every single bug your toddler brings home from daycare. The achy joints that make you feel 20 years older. The average American’s vitamin D is low because we spend so much time indoors, but it does not feel great.

• Ferritin (iron storage)

  • Reference range for women: 12 – 150 ng/mL

  • Optimal range: 50 – 100 ng/mL for women of reproductive age

  • Why it matters: A ferritin of 15 might not get flagged, but it’s miserable. That afternoon crash that has you reaching for your third coffee? That could be low ferritin. The hair you find in clumps in your shower drain that your doctor dismisses as “postpartum shedding” two years later? Likely ferritin. The breathless feeling when you carry your sleeping four-year-old upstairs? I know, we’re not sleeping (and how did he get so big??), but it might be ferritin.

• A1C (avg blood sugar)

  • Reference range: <5.7% = “non-diabetic”

  • Optimal range: 4.8% – 5.3%

  • Why it matters: A 5.6 might seem fine, but it reflects blood sugar spikes and dips that can cause fatigue, anxiety, and hormonal disruption. It’s often an early red flag for metabolic dysfunction. Think hangry mood swings, or 3am wake-ups with your heart racing, even though the baby is asleep.

• CRP (an inflammation marker)

  • Reference range: <3.0 mg/L

  • Optimal range: <1.0 mg/L

  • Why it matters: A CRP of 2.9 means your body is likely in a state of chronic inflammation, but it won't get flagged unless you're off-the-charts inflamed. Subtle inflammation can contribute to fatigue, joint pain, the general feeling your body is working against you, or be the reason you are snapping at everyone…or that could just be because you are literally responsible for too much and what happened to the village??

---

Highlights of the week

Therapy putty: we learned at occupational therapy that therapy putty is basically stealth therapy for kids (and adults!). Kids think they’re just playing with a satisfying squeezable toy when they are actually developing crucial fine motor skills needed to hold pencils properly, and it provides soothing sensory input that helps with focus and emotional regulation. Sidenote, one of my kids skipped crawling and apparently OTs sometimes even prescribe crawling to adults to rebuild foundational coordination and core strength that supports everything from handwriting to attention.

If “A little woo” was a children’s book: I’ve mentioned before that I’m on a quest for kids books that aren’t mind-numbing or don’t have cringey lessons about princesses finding princes. Now, the title of this book is crunchier than I intend, but hear me out: The Barefoot Book of Earth Tales is very lovely. Each story is a folktale from a different country, with rich, visual language and timeless lessons about caring for each other and our world. Think stories about being kind to our neighbors or working together to solve problems. The illustrations are gorgeous, and the stories spark conversations about different cultures and values without being preachy.

Finding a functional medicine provider: I’ve been talking with Chloe, the founder of The Lanby, about how hard it is to find a true ”quarterback” for your health — someone who sees the full picture and connects the dots. The Lanby is one of a small but growing number of practices trying to solve this, blending primary care, functional medicine, and wellness under one roof (here’s their run down of functional bloodwork ranges!). I’m not a patient, but our philosophies are deeply aligned. Other options like Parsley Health or Flora Naturopathics offer similar whole-person, diagnostic-driven care. Unfortunately, none of these models are cheap, because insurance still hasn’t caught up.

---

So if you get labs back that say “you’re fine” but you don’t feel fine, you’re not crazy. The average American doesn’t feel fine. The lab isn’t looking for optimal, it’s looking for not diseased. If you want to feel better than fine, you’re going to need to find someone, and for me it’s a combination of ChatGPT with a functional medicine doctor, to help connect the dots and understand what optimal really looks like. Only then can you start to connect what you’re seeing in your data with how you are actually feeling, and make a plan to feel better. If your labs and your doctor say you’re fine but your body disagrees: listen. That quiet voice isn’t anxiety! It’s data that deserves a different kind of investigation.

I’d love to know if you’ve had similar experiences! Did you know this about reference ranges? Are you surprised?

Joanne

P.S. If you found this post helpful, I’d appreciate it if you <3 it!

If you’re new here:

This is “A little woo,” where I’m exploring why the medical system is losing smart patients, how to advocate for ourselves without losing our minds, and what happens when startup thinking collides with healthcare bureaucracy. Plus, you'll get honest takes on parenting, startups, wellness, and finding your way when the usual playbook isn't working, from a multiple-time startup exec mom who loves science…with a side of woo. Check out my first post Becoming woo for the backstory on why I started this substack or you can read about my personal woo philosophy.