Beyond Basic Bloodwork: What Your GP Isn't Testing

A standard GP check-up covers roughly 8–10 markers: full blood count, liver function, kidney function, basic cholesterol panel. For most clinical purposes, this is sufficient to catch obvious disease.

For anyone focused on performance, optimization, or early detection of suboptimal function — it's nowhere near enough.

Here's what a comprehensive panel adds and why each marker matters.

What the Standard Panel Misses

Free Testosterone (Not Just Total T)

Most GPs test total testosterone only. The problem: a large portion of circulating testosterone is bound to proteins — primarily SHBG (sex hormone binding globulin) — and is biologically inactive. Only free testosterone can actually bind to androgen receptors and produce effects.

You can have total testosterone in the normal range with free testosterone in the gutter, and your doctor will tell you everything is fine. Symptoms of low free T — fatigue, poor recovery, low libido, difficulty building muscle — won't be connected to the bloodwork.

What to ask for: Total testosterone AND free testosterone AND SHBG

SHBG (Sex Hormone Binding Globulin)

SHBG is the binding protein that makes testosterone unavailable. Elevated SHBG is common with:

• High-fibre, plant-heavy diets
• Liver stress
• Thyroid disorders
• Low insulin / very low-carb eating
• Ageing

SHBG isn't tested on a standard panel. Without it, you can't interpret testosterone numbers meaningfully.

Ferritin (Not Just Iron or Hemoglobin)

As covered in the iron deficiency guide: hemoglobin is the last thing to fall in iron deficiency. Ferritin — your stored iron — depletes first and stays low for months or years before hemoglobin is affected.

Low ferritin causes fatigue that doesn't resolve with sleep, hair loss, thyroid conversion problems, poor recovery, restless legs, and cold extremities — all while your doctor says your iron is fine because hemoglobin is normal.

Optimal ferritin: 70–100 ng/mL (most lab normal ranges start much lower)

Vitamin D (25-Hydroxyvitamin D)

Vitamin D deficiency is extremely prevalent — estimates range from 40–70% of adults in northern latitudes, particularly in winter. It presents as fatigue, low mood, immune vulnerability, and impaired muscle recovery.

More critically for men: vitamin D receptors are present in Leydig cells, and adequate vitamin D is associated with significantly higher testosterone. Deficiency suppresses testosterone production.

Optimal range: 50–80 ng/mL (most "normal" ranges flag deficiency only below 20–30 ng/mL)

B12 and Folate

B12 deficiency presents almost identically to iron deficiency — fatigue, brain fog, poor concentration, numbness and tingling (later). It is common in:

• Vegetarians and vegans (B12 is found almost exclusively in animal foods)
• Older adults (impaired absorption with age)
• People on metformin (depletes B12)
• People on PPIs long-term

Folate deficiency causes similar symptoms and also impairs DNA synthesis and cell division, affecting red blood cell production and methylation capacity.

Thyroid Panel (Beyond TSH Alone)

Most standard panels check TSH only. TSH is a pituitary hormone that signals the thyroid — it's an indirect measure. You can have a normal TSH with suboptimal thyroid hormone levels, particularly if you have conversion problems (low T3 despite adequate T4).

What to ask for: TSH, Free T4, Free T3, and ideally anti-TPO antibodies (to screen for Hashimoto's thyroiditis)

ApoB (Apolipoprotein B)

ApoB is a protein present on all atherogenic lipoprotein particles (LDL, VLDL, IDL, Lp(a)). It gives a direct count of the number of atherogenic particles — more predictive of cardiovascular risk than LDL cholesterol alone in most population studies.

Standard cholesterol panels measure LDL cholesterol (the mass of cholesterol carried). ApoB measures the number of particles carrying that cholesterol. Two people with identical LDL cholesterol can have very different particle counts — and very different cardiovascular risk.

hsCRP (High-Sensitivity C-Reactive Protein)

Standard CRP detects overt inflammation. hsCRP is sensitive enough to detect low-grade chronic inflammation — the type associated with cardiovascular risk, metabolic disease, and accelerated aging — even when you feel completely healthy.

hsCRP is also important context for interpreting ferritin (inflammation elevates ferritin, potentially masking deficiency) and for assessing overall inflammatory burden.

The Comprehensive Panel: What to Request

How to Get This Tested

Many GPs will order additional markers if you ask specifically. Some will push back — particularly on free testosterone, ApoB, or extensive thyroid panels — citing "clinical necessity." You can:

• Request explicitly, explaining your symptoms or goals
• Use a private blood testing service (many countries now have direct-to-consumer lab testing)
• Work with a functional medicine physician or longevity clinic that runs comprehensive panels as standard

The difference between a standard panel and a comprehensive one is the difference between knowing you're not sick and knowing how to perform optimally.

Educational content. Not medical advice. Work with a clinician to interpret your specific results in context.