Interpreting Your Bloodwork: Reference Range vs Optimal Range

Have you been told your labs are normal—yet you still have symptoms?

This disconnect often comes down to the difference between the reference range and optional (functional) range on your bloodwork.

REFERENCE RANGE VS. OPTIMAL RANGE

Reference ranges on your bloodwork results are created from the middle 95% of the population. If you fall inside that bell curve, the result is labeled normal.

The problem?
The “average” population includes people with:

• Chronic stress

• Poor sleep

• Inflammation

• Undiagnosed illness

Reference ranges are designed to detect disease, not to reflect how well your body is functioning.

So “normal” often reflects what is common, not what is most healthy.

Optimal ranges are narrower ranges within the reference range based on research, preventative medicine, and real-world symptom improvement—the levels where people tend to feel their best.

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WHAT THIS LOOKS LIKE IN REAL LIFE

Ferritin (iron storage)

• Reference range: ~30-300 ug/L

• Optimal: ~70-100 ug/L

A ferritin of 30 is within the reference range but is commonly linked to fatigue, hair shedding, anxiety, shortness or breath, and restless legs.

If ferritin is consistently >150-200 ug/L (women) and >250-300 ug/L (men), this is linked to inflammation, metabolic, liver, or genetic drivers rather than assuming “great iron levels.”

TSH (thyroid stimulating hormone)

• Reference range: ~0.5-5 mIU/L

• Optimal: ~1-2.5 mIU/L

A TSH of 3.5 does not raise red flags on bloodwork, however, at that level, some patients may experience cold intolerance, constipation, hair shedding, brain fog, or heavy periods.

Vitamin B12

• Reference range: ~130-650 pmol/L

• Optimal: ~400-650 pmol/L

Low-normal B12 can show up as tingling, low mood, poor focus, and low stamina—long before falling out of the low end of the reference range.

Vitamin D

• Reference Range: ~50-200 nmol/L

• Optimal: ~100-150 nmol/L

A vitamin D level of 55 may be labeled as normal, yet still be linked with frequent colds, low mood, muscle aches, fatigue, weak bone, and slower injury recovery. Immunity and hormones need levels within the optimal range to function well year-round.

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SYMPTOMS ARE DATA TOO

Labs are tools used to understand what is going on beneath the surface. In practice, I also consider:

• How you actually feel

• Patterns across multiple markers, interpreting markers against each other

• Trends over time

• Diet, stress, sleep, etc

Two people can have the same number on labs and have two very different lived experiences.

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THIS ISN’T ABOUT OVER-DIAGNOSING

Using optimal ranges is about prevention and function, not labeling everyone with a diagnosis. Sometimes the protocol is nutrition and lifestyle, sometimes it’s targeted supplementation and orthomolecular medicine, and sometimes it’s simply monitoring things (with context).

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HOW I APPROACH LAB REVIEW

1. Compare your results to both the reference and optimal ranges

2. Look for patterns, not numbers in isolation

3. Create a strategic, sustainable plan with you

4. Re-test to assess progress and next steps

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INTERESTED IN A FUNCTIONAL LAB REVIEW?

You deserve healthcare that aims for more than “not sick.”

I order and/or interpret labs through a functional lens—looking beyond “normal” to understand what’s optimal for your symptoms, goals, and long-term health.

If you don't know where to start, don't worry - I do! Book a free consult call to chat with me and learn about how naturopathic medicine might serve you!