If I had a dollar for every woman who told me “my doctor said my labs are all normal, so it’s probably just perimenopause” – I’d have a very specific and depressing fortune.
Here’s the pattern: you feel terrible. You go to your GP. They run the standard panel. Everything comes back “within range.” And because the blood work doesn’t show an obvious problem, the explanation defaults to the most convenient label available – perimenopause, stress, anxiety, or some combination. Nobody looks deeper because the system says there’s nothing to find.
But “within range” and “optimal” are two very different things – and that gap is where a lot of women are being given a label instead of an answer.
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What reference ranges actually are
When your blood test result comes back with a range, say a TSH of 0.5 to 5.0, that range wasn’t designed to tell you where you’d feel your best. It was calculated statistically from a population sample.
The reference range typically represents the middle 95% of results from the people who were tested. That includes people with undiagnosed conditions. It includes people who feel terrible but haven’t been investigated. It includes people on medications that shift their baseline. It includes elderly patients, chronically ill patients, and people who are “fine” by their own report but haven’t felt genuinely well in years.
In other words, the reference range tells you where most people fall. It does not tell you where you should be for your body to function well.
This is why a TSH of 4.2 is “normal” by the reference range but would prompt treatment in some countries and is well above what many endocrinologists consider optimal. The range says you’re fine. Your body says otherwise.
The difference between normal and optimal
Here’s a simplified comparison for some of the most commonly tested markers. These optimal ranges are drawn from functional medicine literature and clinical practice guidelines that prioritise how you feel, not just whether you’re outside a statistical boundary.
TSH (Thyroid Stimulating Hormone) Standard range: 0.5 – 5.0 mIU/L (varies by lab) Optimal: 1.0 – 2.0 mIU/L What to know: A TSH above 2.5 with symptoms is worth investigating further, especially if thyroid antibodies are present. Many labs use a reference range that goes up to 5.0, but the American Association of Clinical Endocrinologists narrowed the recommended upper limit to 3.0 years ago. Plenty of women are sitting at 3.5 or 4.0, told they’re fine, and feeling anything but.
Ferritin (Iron Storage) Standard range: 12 – 150 ng/mL (women) Optimal: 50 – 100 ng/mL What to know: This is one of the biggest gaps between “normal” and “optimal.” A ferritin of 15 is technically within range at most labs, but it’s associated with fatigue, hair loss, brain fog, restless legs, and exercise intolerance. Most women don’t start feeling genuinely better until ferritin is above 50. Yet many GPs won’t flag it until it drops below 12.
Vitamin D (25-hydroxyvitamin D) Standard range: 30 – 100 nmol/L (or 12 – 40 ng/mL depending on the unit) Optimal: 100 – 150 nmol/L (40 – 60 ng/mL) What to know: A level of 35 nmol/L is “normal” by some lab standards but is functionally deficient. Vitamin D is involved in immune regulation (relevant for autoimmune conditions), mood, bone health, and thyroid function. The Endocrine Society recommends levels above 75 nmol/L (30 ng/mL) as a minimum, which is already higher than some lab reference ranges.
Vitamin B12 Standard range: 150 – 900 pmol/L (or 200 – 1100 pg/mL) Optimal: 400 – 800 pmol/L (500 – 1000 pg/mL) What to know: B12 deficiency causes fatigue, brain fog, tingling, mood disturbances, and memory problems. A level of 180 pmol/L is “within range” but is associated with neurological symptoms. Many practitioners won’t consider supplementation until you drop below 150, by which point you may already have nerve damage. Japan and some European countries set their lower limit at 500 pg/mL.
Fasting Insulin Standard range: 2.0 – 25.0 mU/L Optimal: 2.0 – 8.0 mU/L What to know: This test is rarely ordered by GPs unless you’re already diabetic, but it’s one of the most useful metabolic markers available. A fasting insulin of 18 is “normal” by the lab range but indicates significant insulin resistance — which connects to weight gain, fatigue, PCOS, inflammation, and difficulty losing weight despite doing everything “right.” By the time fasting glucose is elevated (what most GPs do test), insulin has often been high for years.
CRP (C-Reactive Protein) Standard range: 0 – 5.0 mg/L (sometimes up to 10) Optimal: Below 1.0 mg/L What to know: CRP is a general inflammation marker. A reading of 3.0 is “normal” by most lab standards but tells you there’s low-grade systemic inflammation happening. The research linking CRP above 1.0 to cardiovascular risk and chronic disease is extensive. High-sensitivity CRP (hs-CRP) is the more useful version of this test.
Why your doctor isn’t catching this
I want to be fair to GPs here, because most of them aren’t being negligent, they’re working within a system that wasn’t designed for nuance.
General practitioners are trained to screen for disease, not optimise function. Their job, as the system defines it, is to identify whether you have a diagnosable condition that requires treatment. If your TSH is 4.0, you don’t meet the diagnostic criteria for hypothyroidism by most guidelines. The fact that you’d feel noticeably better at 1.5 isn’t part of the equation.
They’re also working under enormous time pressure. The average GP consultation in Australia is 15 minutes. That’s enough time to order a standard panel, check the results against the lab’s flagging system (which only flags results outside the reference range), and tell you everything looks fine. It’s not enough time to sit down and say “your ferritin at 18 is technically within range but let’s talk about why you’re losing hair.”
And the lab reports themselves are part of the problem. Results are literally colour-coded: green for normal, red for abnormal. If nothing is red, the report says you’re fine. The system is designed around flags and thresholds, not gradients and patterns.
What you can do about it
Request a copy of your actual results. Don’t accept “everything’s fine” over the phone. Get the numbers. In Australia, you have the right to access your own pathology results. Most labs also have online portals where you can view them directly.
Compare to optimal ranges, not just the lab range. Use the ranges above as a starting point. If something is “in range” but sitting near the bottom or top of the reference range, and you have symptoms that match, that’s worth a conversation.
Track your results over time. A single blood test is a snapshot. Trends tell you much more. A ferritin that was 45 last year and is 22 this year is heading in a concerning direction, even though both numbers are “normal.” Ask your doctor to compare to previous results.
Don’t be afraid to ask for specific tests. “I’d like to add ferritin, vitamin D, and fasting insulin to my next blood panel” is a reasonable request. If your GP pushes back, ask them to document the refusal in your file (this often changes the conversation).
Consider seeing a practitioner who works with optimal ranges. Functional medicine doctors, integrative GPs, and some naturopaths work with tighter ranges and are more likely to investigate the grey zone between “normal” and “optimal.” This doesn’t mean abandoning your GP, it means adding someone to your team who looks at the data differently.
The bottom line
“Normal” is not a diagnosis. And “perimenopause” is not an explanation when nobody’s actually investigated what’s driving your symptoms.
If your labs are “normal” but you feel terrible, you’re not imagining things. You might be sitting in the gap between the reference range and where your body actually needs to be. And that gap is worth exploring — thoroughly — before accepting any label as a final answer.
Bold Leap provides health education, not medical advice. The optimal ranges discussed here are drawn from functional medicine literature and are not universally agreed upon. Always work with a qualified healthcare provider when interpreting your blood work and making health decisions.
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