Five Tests That Catch Insulin Resistance Years Before Your Doctor Will
- Jul 30
- 9 min read
Dr. Michael Donaldson is a nutrition researcher and health coach specializing in type 2 diabetes reversal. As founder of End Diabetes Now and Research Director at Hallelujah Diet, he empowers people to transform their health through evidence-based, plant-centered nutrition.
Your doctor said your labs are normal, but you don't feel normal. You don't have the energy you used to. You carry extra weight that won't go away. Your thinking isn't as clear. You don't recall names as well.
The problem isn't that you're just getting older or that there isn't a problem at all. The problem is that it is going undetected. The wrong tests are being ordered, and the right calculations are never made using the numbers you do get. Here are three markers your doctor almost never orders and two calculations that could be run using the data already sitting in your chart.
All of these are capable of catching insulin resistance and metabolic dysfunction years before your standard blood work will. Pay attention, and you could learn the answer to why you don't feel normal.
I have spent nearly three decades studying health and learning why metabolic disease develops. One pattern that shows up quite often involves people who feel off, with low energy, mental fog, and stubborn weight gain, but have normal fasting glucose. It may be a little elevated, but it is still normal. This isn’t a good pattern because fasting glucose is often one of the last markers to become elevated. By the time it rises, insulin resistance may have been building silently for 10 years or more.
The five markers I'm going to walk you through fall into two categories.
The first consists of lab tests that your doctor doesn't order. The second consists of information derived from numbers in your lab results, but it is just sitting there because the numbers aren't put together to tell the whole story.
These are routine tests and calculations, not exotic or expensive. You just have to know how to order the right tests.
Markers your doctor almost never orders
Test 1: Fasting insulin, the marker your annual panel is missing entirely
Standard annual labs measure fasting glucose. They almost never measure fasting insulin.
It's a little like looking at the oil pressure gauge in your car to see if your engine has enough oil. By the time your engine loses oil pressure, it has lost almost all the oil in the system. You need to read the dipstick to see if you have enough oil in your car.
Fasting glucose is just like that. Glucose levels are like oil pressure. Oil pressure is the wrong test to see if your engine has oil, and glucose is the wrong test to see if your metabolism is okay. The dipstick for your metabolism is fasting insulin.
Fasting insulin tells you how hard your pancreas is working to keep blood glucose levels normal. When cells become resistant to insulin's signal, the pancreas produces more insulin to force the cells, especially those in your liver and muscles, into submission. Glucose levels stay normal, but insulin levels may be three to four times the optimal level. That's insulin resistance. Fasting insulin reveals it right away, but it isn't measured on a standard lab panel.
Dankner et al. followed 515 normoglycemic adults for 24 years and found that elevated fasting insulin, independent of BMI, blood pressure, triglycerides, and fasting glucose, was the single strongest predictor of who would eventually develop type 2 diabetes. Nearly a quarter of that group progressed all the way to diabetes. Their insulin was the early signal, years before their glucose levels were abnormal.
A 2016 reanalysis of Kraft's original database by Crofts et al., published in *Diabetes Research and Clinical Practice*, confirmed that hyperinsulinemia, meaning high levels of insulin after eating or during a glucose tolerance test, appears in nearly 75% of people with completely normal glucose tolerance. Most of them had no other clinical symptoms. Fasting insulin won't catch every case, but it will catch the metabolic direction, and that's what matters if your goal is optimal function, not just avoiding a diagnosis.
A fasting insulin above 8 mIU/L is a warning sign worth investigating. Optimal is below 6 mIU/L. The Quest Diagnostics reference range is 2.1 to 9.0 mIU/L. Labcorp’s reference range is 2.6 to 24.9 mIU/L, a range so broad that it includes many people with metabolic dysfunction.
What is HOMA IR, and why does the calculation matter?
HOMA IR, or Homeostatic Model Assessment of Insulin Resistance, combines both numbers: fasting insulin in mIU/L multiplied by fasting glucose in mg/dL, divided by 405. You need both values to run it. Most doctors order one without the other.
Here's what the numbers mean in practice. A fasting insulin of 5 mIU/L and a fasting glucose of 85 mg/dL give you a HOMA IR of about 1.0. That's optimal. Below 1.5 is the target range. Below 2.0 is acceptable. At 2.5 and above, insulin resistance is present.
Isokuortti et al. found the upper 95th percentile of HOMA IR in a population of more than 1,600 healthy Finnish adults to be 1.9, meaning that even what the research community calls the boundary of “normal” sits above optimal. As with fasting insulin, the reference range isn't protecting you.
The calculation predicts real outcomes. González González et al. published a systematic review and meta-analysis in 2022 covering 38 studies and 215,878 participants. They found that elevated HOMA IR was associated with an 87% increased risk of developing type 2 diabetes, a 46% increased risk of nonfatal cardiovascular events, and a 35% increased risk of hypertension. HOMA IR gives you valuable information connected to real health outcomes. The barrier is that most doctors never order fasting insulin, so the calculation never gets made.
Test 2: ApoB, your lipid panel counts cholesterol, this counts what actually damages arteries
Your standard lipid panel reports LDL C, the concentration of cholesterol carried in LDL particles. What it doesn’t report is how many LDL particles are actually circulating. That’s what ApoB measures.
Every atherogenic particle carries exactly one ApoB protein, so ApoB is a direct particle count. You can have a normal LDL C and a dangerously high particle number, especially when insulin resistance drives the production of smaller, denser particles that carry less cholesterol per particle but cause more arterial damage per collision. LDL C tells you the cargo. ApoB counts the trucks.
Sniderman et al. made exactly this argument in *The Lancet* in 2003. ApoB is a superior index of coronary risk compared with LDL C, particularly in people with metabolic syndrome, because it directly counts the atherogenic particles rather than estimating the cholesterol they carry.
ApoB is not on a standard annual panel. If your triglycerides are elevated and your HDL is low, which is quite common in insulin resistance, your ApoB is likely elevated regardless of what your LDL C says. Most doctors won’t order it to find out.
Test 3: Uric acid, an early warning signal for metabolic dysfunction that almost nobody orders
Uric acid is almost never ordered unless a doctor suspects gout. That’s too narrow. Elevated uric acid is one of the earliest detectable signs of metabolic dysfunction, often rising years before fasting glucose does.
Uric acid is the direct metabolite of cells consuming large amounts of fructose. Johnson et al. laid out the full mechanistic case in a 2009 review in Endocrine Reviews.
It works like this: Excessive fructose intake raises uric acid. Uric acid impairs nitric oxide production in blood vessel walls, reduces insulin signalling, and raises blood pressure. This cascade contributes directly to metabolic syndrome and type 2 diabetes. Globally, fructose intake is closely associated with diabetes rates. The mechanism runs through uric acid.
The “normal” range for uric acid typically goes up to 7.0 mg/dL for men and 6.0 mg/dL for women. However, metabolic risk begins climbing above 5.5 mg/dL in both sexes. A result of 6.2 mg/dL won’t trigger a flag on your lab report. In metabolic terms, it’s an early signal that something is happening upstream, before your glucose even moves.
If your diet is high in fructose from processed foods, sweetened beverages, or excessive fruit juice, your uric acid will likely be in the higher range.
Calculations your doctor already has the data to run, but never does
The next two markers don’t require an additional blood draw. The numbers are already in your results. What’s missing is the decision to do the math.
Calculation 1: The triglyceride to HDL ratio, your lipid panel has the answer, but nobody divides it
Most people with a standard lipid panel already have the two numbers needed to calculate one of the most reliable noninvasive markers of insulin resistance. The triglyceride to HDL ratio is almost never calculated or communicated to the patient.
McLaughlin et al. tested multiple metabolic markers against gold standard insulin clamp measurements in 258 adults and found that the triglyceride to HDL ratio was among the most useful for identifying insulin-resistant individuals. A ratio above 3.0 in traditional US units, measured in mg/dL, identified insulin resistance with 64% sensitivity and 68% specificity. This was comparable to the full Adult Treatment Panel III metabolic syndrome criteria and achievable using two numbers already on your lipid panel. Nobody calculates it.
Your total cholesterol could look fine. Your LDL could look fine. However, if your triglycerides are 180 and your HDL is 42, your ratio is 4.3, and that tells a very different metabolic story from what appears on your lab report.
Optimal fasting triglycerides are below 100 mg/dL. Most labs don’t flag anything until 200 mg/dL. If your triglycerides are between 100 and 150, that’s a metabolic signal worth addressing now.
Calculation 2: PhenoAge, your biological age, calculated from existing lab data
Have you ever seen a 50-year-old woman who looks 35? On the other hand, have you seen a 50-year-old woman who looks 75? There are ways to estimate someone’s biological age based on what is happening inside the body, which we can sometimes see reflected on the outside.
To me, this calculation is the most fascinating and striking. You can really tell whether you're winning the war against ageing with this calculation. Nine biomarkers that appear in a standard blood panel- albumin, creatinine, glucose, C-reactive protein, lymphocyte percentage, mean cell volume, red cell distribution width, alkaline phosphatase, and white blood cell count- can be combined into a single calculation that estimates your biological age.
Morgan Levine and colleagues at Yale developed the PhenoAge algorithm using NHANES III data from 9,926 adults, applying a penalised regression model to narrow 42 candidate biomarkers down to the nine mentioned above that best predicted mortality risk. Those nine biomarkers produce a single number: your biological age.
The validation data tell a clear story. In a follow-up cohort of 6,209 nationally representative US adults tracked for up to 12 years, each one-year increase in PhenoAge above chronological age was associated with a 9% increase in all-cause mortality risk, a 10% increase in cardiovascular mortality risk, and a 20% increase in diabetes mortality risk. The authors noted that the clinical biomarker-based PhenoAge is a better predictor of morbidity and mortality than more complex laboratory measures.
Every number needed to calculate your PhenoAge is already on your standard blood work. Your doctor has the data. The calculation is never made.
“Normal” is not the same as “healthy”
Every laboratory has a reference range based on what it normally sees in the population, and values outside that range are flagged. However, “normal” is not the same as “optimal.” It is simply what is statistically common in a population.
When the average person is sick and overweight, “normal” does not mean much. For example, fasting insulin up to 25 mIU/mL is “normal.” Uric acid up to 7.0 mg/dL is “normal.” Triglycerides up to 150 mg/dL are within the reference range, meaning “normal.” These ceilings don't reflect optimal metabolic function. They simply reflect what is common.
PhenoAge makes this argument very clear. If your biological age is three years older than your chronological age, that won't show up as a flag on a standard lab report, but it should set off an alarm bell that your body is ageing faster inside than the calendar is passing by.
When I look at these markers with people, I'm not just looking to see if the results are “normal” or even “optimal.” I'm trying to get an idea of your metabolic trajectory. That is, where are you headed, not just where are you today? What do all these numbers mean? If you keep going in the same direction you’ve been going, without taking action to become healthier, what will happen?
What should you do with this information?
Start with a conversation with your doctor. Ask them to order fasting insulin alongside your next fasting glucose test. Ask for your triglyceride-to-HDL ratio to be calculated. Ask whether ApoB and uric acid are included in your panel. Ask your doctor to run those tests.
For PhenoAge, you can calculate your biological age right now if you have recent blood work. The nine biomarkers needed are included in most standard panels.
You'll find a free, accurate calculator here. If your biological age is ahead of your chronological age, you should take action.
I offer a comprehensive metabolic assessment that includes all five of these markers and calculations, along with 80 additional biomarkers. It is specifically designed for people who’ve been told their labs are fine but don’t feel fine. If you want to know what your numbers actually mean, you can learn more about that assessment here.
You’ve spent years building a life with real purpose. Your body is supposed to give you the energy and strength to live it fully. The right tests and the right calculations are the first step towards understanding what’s actually standing in the way.
Read more from Michael Donaldson
Michael Donaldson, Nutrition Researcher & Health Coach
Dr. Michael Donaldson, Ph.D., is a leading voice in plant-based nutrition and lifestyle transformation. With a doctorate from Cornell University and more than two decades of research at Hallelujah Diet, he has helped thousands understand how food can restore health and vitality. Through his coaching platform End Diabetes Now, he guides clients in reversing type 2 diabetes naturally and sustainably. A scientist, entrepreneur, and educator, Dr. Donaldson also founded True Wealth Health Products and formulated Ora-Shield, an organic oral-care blend. His work bridges science, faith, and practical wisdom to help people achieve lasting wellness and purpose.
