Measuring metabolic health: the blood values your doctor often skips

You feel great. You train four times a week, you sleep reasonably well, your weight is stable. Then you drop by your doctor for a routine test, and the result comes back with the standard line: 'everything looks fine'. Sounds reassuring. But the real question is: is 'fine' the same as optimal? And more importantly, what did that test actually not measure?

This is exactly where metabolic health goes wrong. A standard blood test at the GP is built to detect disease, not to give you direction when you want to optimise. The system waits until something is broken. You want to know which way things are moving, years before anything breaks. Those are two completely different goals, and they call for different markers.

Why a standard GP test misses the early signals

Picture your metabolic health as a road surface. A standard test checks whether there is already a pothole. The markers you really want to see feel the first hairline cracks, sometimes five to ten years before the hole appears. That difference in timing is everything when your goal is prevention and performance rather than damage repair.

Take blood sugar. Most doctors measure fasting glucose and assume a normal value means your sugar handling is in order. But your body is a master at masking problems. Long before your glucose rises, your pancreas works overtime to keep that glucose low. The result: a normal glucose, but a sharply elevated insulin in the background. The Diabetes Fonds has long pointed out that insulin resistance can build up unnoticed for years before a diagnosis of prediabetes or diabetes lands. A test that only measures glucose simply does not see that underwater period.

The same goes for your heart. The GP usually looks at total cholesterol and maybe LDL. But those numbers do not tell you how many cholesterol particles can actually push into your blood vessels. For that you need a different marker, and it is rarely on the standard lab request form by default. I think this is one of the biggest blind spots in mainstream care: we have been measuring the wrong number for decades while a better alternative exists.

The five metabolic domains and the marker that picks each up earliest

Metabolic health is not a single number. It is a few interconnected systems: how you process fats, how you process sugar, how you balance growth and recovery, and how much silent inflammation runs under the hood. For each domain there is a marker that gives the first signal. This table is your decision aid.

1. ApoB: the heart risk marker that is usually missing

If there is one marker that deserves more attention, it is ApoB. Every harmful cholesterol particle, whether LDL, VLDL or another particle, carries exactly one ApoB molecule. Count those particles, and you know how many 'bullets' are flying towards your artery wall. Two people with exactly the same LDL can have a totally different particle count, and therefore a totally different risk. The Hartstichting stresses that an unfavourable cholesterol profile is a major risk factor for cardiovascular disease; ApoB makes that profile sharper to measure than LDL alone. If you want to dive deeper into the numbers, read our spoke on ApoB as a heart risk marker.

Broadly speaking, people who want to optimise often aim for an ApoB well below the population average, because lower tends to be more favourable here. What counts as a sensible target for you depends on your overall risk profile and is something to discuss with a doctor.

2. Fasting insulin: reading your sugar handling years earlier

This may well be the most underrated marker on this list. Fasting insulin shows how hard your pancreas has to work to keep your blood sugar stable. A low, healthy insulin value means your body handles sugar efficiently. An elevated value, while your glucose is still normal, is often the very first sign that insulin resistance is building. That window, sometimes years wide, is precisely where you can change something in your lifestyle before it becomes difficult.

Combine fasting insulin with fasting glucose and you can calculate HOMA-IR, a simple index of insulin sensitivity. We explain that calculation and its interpretation step by step in our spoke on fasting insulin and HOMA-IR. For the value itself, see fasting glucose alongside your insulin.

3. HbA1c: the long-term memory of your blood sugar

Where fasting glucose is a snapshot, HbA1c is the average of your blood sugar over the past two to three months. That makes it less sensitive to what you ate yesterday or how stressed you were during the draw. For anyone tracking metabolic health seriously, an HbA1c creeping towards the top of the normal range is already a signal to stay alert, even if the result is not formally flagged as abnormal yet. Normal and optimal are not the same thing here. What a value means when you do not have diabetes is covered in the spoke on HbA1c in non-diabetics.

4. IGF-1: the balance between growth and longevity

IGF-1 reflects the action of your growth hormone. For athletes, more growth hormone sounds immediately appealing: more muscle building, better recovery. And an IGF-1 that is too low can indeed hold back recovery and muscle retention. But there is a flip side: chronically high IGF-1 values are linked in research to a potentially less favourable longevity profile. So it is not a question of 'higher is better', but of the right balance for your goals. We work out that nuance fully in our spoke on IGF-1 explained.

5. Triglycerides, HDL and fatty acid status

The ratio between your triglycerides and your HDL is one of the cheapest and most underrated windows on insulin resistance. A high ratio can point to a metabolism that struggles with sugar, often before your glucose or HbA1c gives it away. On top of that, your omega-3 index tells you how much of those beneficial fatty acids are actually built into your cell membranes. Low values may be linked to more silent inflammation and slower recovery after hard training. We go deeper into this in the spoke on the omega-3 index. If you want to know whether a marker also picks up inflammation: hs-CRP and LDL together with the markers above give a more complete picture.

Normal versus optimal: the difference that gives you direction

This is the core idea behind the whole approach. A laboratory reference range is based on the spread in the population, not on what is optimal for performance and health. If a large part of the population is not in metabolic top form, then 'normal' partly describes that very suboptimal state. Within normal you can still optimise considerably.

A concrete example makes the difference tangible. Two athletes both have a fasting glucose of 5.3 mmol/l, formally perfectly normal. But one has a fasting insulin of 4 mIU/l and the other of 14 mIU/l. On paper they are equal, in reality the second has been under pressure for years to keep that glucose low. That is exactly the distinction you miss if you sail on the standard values alone, and exactly the distinction that steers you towards a different lifestyle choice.

The Gezondheidsraad stresses the importance of prevention and a healthy lifestyle as the foundation of public health. Optimising based on your own markers fits exactly within that preventive idea: you act on trends before they become clinical problems. It remains important that a target value is not a diagnosis. What is healthy for you depends on your age, sex, training load and medical history, and is something to discuss with a doctor.

What you concretely do with this

Numbers without action are useless. So here are a few concrete steps if your markers drift towards the less favourable side.

• Elevated fasting insulin or triglyceride/HDL ratio: take a critical look at fast carbohydrates and alcohol, and build in more movement after meals. Strength training improves your insulin sensitivity considerably. The Voedingscentrum offers practical, reliable guidelines for a fibre-rich, less processed diet that helps here directly.
• ApoB on the high side: replacing saturated fat with unsaturated fat and adding more soluble fibre can make a difference. With sharply elevated values, this conversation belongs with your doctor.
• Low omega-3 index: more oily fish or a targeted supplement can visibly improve your index over a few months. Retesting shows whether it works.
• HbA1c creeping up: the same lifestyle levers as with insulin, plus attention to sleep and stress, which affect your blood sugar more than many people think.

The power lies in repeated measurement. One measurement is a photo, a series of measurements is a film. Only when you track your markers over time do you see whether a change in your training or nutrition actually moves the needle. That is how you optimise: measure, intervene, measure again.

How to get these markers tested

You do not have to wait until your GP happens to tick the right boxes. Many of these markers you can have measured in a targeted way and without a referral. A lipid panel maps your fat profile as a basis for your heart health. If you want a broader look at your hormonal balance and recovery, a general hormones panel gives more context. If you are specifically tracking your testosterone and recovery during a programme, TRT monitoring fits there, and you check your kidney function with kidney health if you train intensively or use supplements.

Combine these insights with the spokes in this cluster and you build a complete picture step by step. Start, for example, with how fasted training affects your blood sugar and hormones, what happens on a keto diet, or how you retain muscle mass while losing weight with GLP-1. Each of those choices leaves its mark on exactly the markers we discussed above.

Metabolic health is not a matter of luck, it is a matter of insight. The right markers give you that insight years before a standard test picks up anything at all. That is the difference between reacting to problems and steering towards your next level. The choice of which way to steer is yours, and you make it best in consultation with a doctor who reads your data alongside you.

Further reading

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