Your blood test is normal but you are still tired…

Laboratories determine the “reference range” based on the results of 95% of the population.

This is a statistical average, not a health standard.

For example, the lower limit for B12 may be 200–250 pg/mL, but many people experience fatigue, forgetfulness, and dizziness below 350. (British Journal of Haematology, 2023)

What is a functional deficiency?

Even if the blood level of a particular vitamin, mineral, or hormone is within normal limits, the cells' ability to utilize these substances may be reduced. This is called a "functional deficiency."

For example:

- Iron: Ferritin is normal but oxygen carrying capacity is low.

- Vitamin D: Blood levels are sufficient, but vitamin D receptors in the tissues are insufficient.

- Magnesium: Serum value is normal but intracellular magnesium is low.

3 things you can try today

1 - Gather your blood tests of the last year: See them in a single table, check if there is a downward trend.

2 - Set the optimal level target: Take note of the “best” value for you, not just the “normal” one.

3 - Schedule a follow-up test: If functional deficiency is suspected, request an intracellular mineral or MMA test.

Effects on daily life

In people with functional deficits:

- Waking up tired in the morning,

- Energy drop in the middle of the day,

- Memory and focus problems,

- Frequent infections,

- Mood swings

Complaints such as these are common. This condition can be confused with depression, chronic fatigue syndrome, or anemia.

Functional health approach

This approach seeks to answer not only the question “are there any deficiencies?” but also “what is the optimal level?”

For example, the optimal B12 level is much higher than the laboratory lower limit (500–800 pg/mL). Similarly, the optimal range for vitamin D is recommended as 40–60 ng/mL. (Cleveland Clinic Functional Medicine, 2023)

The most commonly confused diseases

Functional deficiencies may be misdiagnosed because they have similar symptoms to other diseases:

- Depression with hypothyroidism

- Chronic fatigue syndrome with anemia

- Fibromyalgia with magnesium deficiency

- Osteoporosis due to vitamin D deficiency

Misdiagnosis may lead to unnecessary medication being prescribed or the real problem being overlooked.

Which nutrients maintain optimal levels?

- B12: Red meat, eggs, dairy products, fish

- Iron: Red meat, lentils, spinach (with vitamin C)

- Magnesium: Almonds, hazelnuts, green leafy vegetables

- Vitamin D: Oily fish, egg yolk, sunbathing

- Iodine: Seafood, iodized salt

Risks of incorrect treatment

- Unnecessary thyroid hormone production → Heart palpitations, osteoporosis

- Iron overload → Liver damage, joint pain

- High dose vitamin D → Kidney stones, vascular calcification

- Unnecessary antidepressants → Side effects + not solving the main problem

Case history

A 54-year-old woman used antidepressants for 2 years because of persistent fatigue and depression.

The medicine didn't help.

Detailed tests revealed a B12 level of 280 pg/mL (normal according to the lab).

B12 treatment was started with a functional medicine approach, and within 3 months, complaints of fatigue and depression decreased significantly.

What further tests can be performed?

- Intracellular mineral analysis: Clearly shows magnesium, potassium and zinc levels.

- Methylmalonic acid (MMA): Catches B12 deficiency at an early stage.

- Homocysteine: It is a sign of folate and B12 deficiency.

- 25(OH)D and 1.25(OH) ₂D together: Shows both steps of vitamin D metabolism.

- Thyroid antibodies (anti-TPO, anti-Tg): Detects autoimmune thyroid disease early.

5 values ​​that may appear normal in blood but low in tissue

1 - Vitamin B12: Measuring “holotranscobalamin” instead of serum may be more accurate.

2 - Iron: Ferritin + transferrin saturation should be evaluated together.

3 - Magnesium: Intracellular magnesium measurement should be made.

4 - Vitamin D: The active form (1.25(OH)₂D) may decrease in some patients.

5 - Thyroid hormone: While TSH is normal, free T3 may be low. (Journal of Clinical Laboratory Analysis, 2024)

TOMORROW:

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