2 June 2026 · Chris Carpenter
The five blood tests your GP probably isn't running — and why they matter
If you’ve ever had a blood test come back normal and still felt like something was wrong, this post is for you.
The standard NHS blood panel is designed to catch disease once it’s already established. It is not designed to reveal the decade of metabolic deterioration that precedes diagnosis. By the time your results cross the threshold into “abnormal,” the damage has been building for years.
There are five markers that tell a far more complete story. Most GPs don’t order them routinely. Some aren’t available on the NHS at all. But if you want to know where you actually stand metabolically — not where you’ll stand in ten years when the standard markers finally tip — these are the ones to know about.
1. Fasting insulin
This is the single most important metabolic marker most people have never had tested.
Fasting glucose — the test you almost certainly have had — tells you what your blood sugar is doing right now. Fasting insulin tells you how hard your pancreas is working to keep that number normal. And it is entirely possible to have a perfectly normal fasting glucose while your fasting insulin is significantly elevated — meaning your pancreas is compensating hard, insulin resistance is already well established, and the system is under serious strain.
Normal fasting glucose with high fasting insulin is not a clean bill of health. It is an early warning that the standard test is missing.
What to aim for: fasting insulin below 8 mIU/L is considered optimal by many metabolic health researchers. Above 15 mIU/L suggests significant insulin resistance even if blood glucose is normal. The NHS does not include this in a standard panel — you may need to request it specifically or test privately.
2. HOMA-IR
HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It sounds complicated. It isn’t.
It’s a calculation derived from your fasting insulin and fasting glucose that produces a single number representing your degree of insulin resistance. You don’t need a separate test for it — if you have both fasting insulin and fasting glucose results, you can calculate it yourself or use any online HOMA-IR calculator.
What to aim for: below 1.0 is optimal. Between 1.0 and 1.9 suggests early insulin resistance. Above 2.0 indicates established insulin resistance. Above 2.9 is associated with significant metabolic dysfunction.
This single number gives you more actionable information about your metabolic health than most standard blood panels combined.
3. Triglyceride to HDL ratio
This one is hiding in plain sight. Triglycerides and HDL cholesterol are both measured on a standard lipid panel — the blood test most people have had. But most people are only told whether the individual numbers are “in range.” The ratio between them is rarely discussed.
The triglyceride to HDL ratio is one of the most reliable proxy markers for insulin resistance available from a standard blood test. High triglycerides are driven largely by excess carbohydrate intake and elevated insulin. Low HDL is associated with the same metabolic dysfunction. When triglycerides are high and HDL is low, the ratio signals significant insulin resistance even when other markers look acceptable.
How to calculate it: divide your triglyceride number by your HDL number. Both should be in the same unit — mmol/L if you’re in the UK.
What to aim for: below 1.0 is optimal. Above 1.5 suggests insulin resistance. Above 2.0 is a strong signal of significant metabolic dysfunction.
If your GP has given you a lipid panel result, you can calculate this right now.
4. HbA1c — but in context
HbA1c is the marker most commonly used to diagnose prediabetes and type 2 diabetes, and it is likely the one you’re most familiar with. It measures your average blood glucose over the previous two to three months by looking at how much glucose has attached to red blood cells.
It’s a useful marker. But it has limitations that are rarely explained.
HbA1c can be normal — technically in the non-diabetic range — while fasting insulin is elevated and insulin resistance is already well established. It is also affected by factors unrelated to blood sugar, including red blood cell turnover, iron deficiency anaemia, and certain genetic variants. A normal HbA1c is reassuring but not conclusive.
The most useful way to read HbA1c is alongside fasting insulin and the triglyceride to HDL ratio. Together they give a complete picture. In isolation, HbA1c tells you where you are on one axis of a multi-dimensional problem.
What to aim for: below 39 mmol/mol (or 5.7% in the older measurement) is considered non-diabetic. But optimal metabolic health is associated with results below 35 mmol/mol — a target most standard panels wouldn’t flag as requiring any attention.
5. High-sensitivity CRP (hs-CRP)
Insulin resistance doesn’t just affect blood sugar and fat storage. It drives chronic, systemic inflammation — and chronic inflammation accelerates virtually every degenerative disease process, from cardiovascular disease to cognitive decline.
High-sensitivity CRP is a marker of systemic inflammation. It is more sensitive than standard CRP and can detect low-grade chronic inflammation that a routine test would miss entirely.
Elevated hs-CRP in the context of other metabolic markers is a strong signal that insulin resistance has been present long enough to trigger an inflammatory response — and that the consequences are already beginning to spread beyond the metabolic system.
What to aim for: below 1.0 mg/L is optimal. Between 1.0 and 3.0 mg/L indicates moderate risk. Above 3.0 mg/L suggests significant chronic inflammation.
What to do with this information
If you want to get these markers tested, you have a few options.
Ask your GP directly. You may not get all five on the NHS, but it is worth asking — particularly for fasting insulin and hs-CRP. If your GP is aware of your metabolic concerns and your family history, some of these may be available.
Test privately. Companies like Medichecks or Thriva in the UK offer comprehensive metabolic panels that include all five of these markers. Costs vary but a full panel is typically available for under £100.
Once you have the results, bring them back here — or better still, bring them to a conversation with someone who can help you interpret them in the context of a protocol designed to move all five markers in the right direction.
That is exactly what the Feel Great System is designed to do. Not manage the numbers with medication, but address the hormonal root cause so the numbers improve because the underlying condition is improving.
