Triglyceride to HDL Ratio Calculator
Triglyceride to HDL Ratio Calculator
Divide triglycerides by HDL cholesterol in mg/dL as a surrogate for insulin resistance and small dense LDL — and see why the same thresholds cannot be used in mmol/L.
Triglyceride to HDL Ratio
TG ÷ HDL → ratioTriglycerides 130 mg/dL, HDL cholesterol 48 mg/dL
Formula
mg/dL = mmol/L × 88.57 for triglyceride, × 38.67 for cholesterol
- mg/dL only
- unlike the cholesterol ratio, this one is unit-dependent: triglyceride and cholesterol convert with different factors, so the units do not cancel
- × 2.3
- the same sample gives a ratio about 2.3 times smaller in mmol/L than in mg/dL, because 88.57 ÷ 38.67 ≈ 2.29
- surrogate
- the ratio tracks insulin resistance and small dense LDL indirectly; it measures neither
Worked example
Triglycerides 130 mg/dL, HDL cholesterol 48 mg/dL
130 ÷ 48 = 2.71
Between 2.0 and 3.5 → intermediate
The same sample in mmol/L (1.47 and 1.24) gives 1.18 — the mg/dL thresholds do not apply to it
Thresholds, and their mmol/L equivalents
| Category | Ratio in mg/dL | Equivalent ratio in mmol/L |
|---|---|---|
| Low | < 2.0 | < 0.87 |
| Intermediate | 2.0 – 3.5 | 0.87 – 1.53 |
| High | > 3.5 | > 1.53 |
What the ratio is and is not evidence for
| Question | Answer |
|---|---|
| Does a high ratio indicate insulin resistance? | It is associated with it, and performs reasonably as a screening surrogate in the populations studied |
| Does it diagnose insulin resistance? | No — the reference methods are the euglycaemic clamp and, less formally, HOMA-IR |
| Does it apply to people of African ancestry? | Poorly — triglycerides are lower at the same degree of insulin resistance, so the ratio under-detects |
| Is there a guideline threshold? | No. The 2.0 and 3.5 cut-offs come from cohort studies, not from a guideline |
A unit-dependent ratio with a population limit
The first thing to check is the unit. Unlike the total cholesterol to HDL ratio, this one is not dimensionless in any useful sense: triglyceride and cholesterol are different molecules with different molecular weights, so they convert between mass and molar units with different factors — 88.57 for triglyceride and 38.67 for cholesterol. The same sample therefore yields a ratio about 2.3 times smaller when both values are in mmol/L than when both are in mg/dL. Every threshold in general use, including the 2.0 and 3.5 cut-offs here, is a mg/dL threshold, and applying it to an mmol/L ratio makes almost everyone look low-risk.
What the ratio is used for is a rapid surrogate for insulin resistance and for the small dense LDL phenotype. The physiology behind it is coherent: insulin resistance drives hepatic VLDL overproduction, raising triglycerides, and the resulting triglyceride-rich particles fuel cholesteryl ester transfer that depletes HDL and remodels LDL into smaller, denser and more atherogenic particles. The two terms of the ratio therefore move in opposite directions in the same process, which is why dividing one by the other separates people more sharply than either does alone.
The most important limitation is who it was validated in. The ratio was derived and tested largely in white populations, and it performs poorly in people of African ancestry, who have lower triglyceride concentrations at any given degree of insulin resistance. A Black patient can be substantially insulin resistant with a triglyceride to HDL ratio that looks entirely reassuring, so a low ratio should not be used to rule out insulin resistance in that setting.
Even where it performs well, it is not a diagnostic test. Insulin resistance is defined against the euglycaemic hyperinsulinaemic clamp and estimated in practice by HOMA-IR or by direct glycaemic measures, and no guideline recommends the ratio for the purpose. Published cut-offs also drift between cohorts, roughly from 2.0 to 3.8, depending on the population and the outcome being predicted. Treat a raised ratio as a prompt to assess glycaemia, weight, blood pressure and the rest of the lipid profile properly, not as a conclusion.
Frequently asked questions
What is a normal triglyceride to HDL ratio?
Below 2.0 in mg/dL is generally considered low, 2.0 to 3.5 intermediate, and above 3.5 high. These figures apply only to values measured in mg/dL.
Can I use these thresholds if my results are in mmol/L?
No. Triglyceride and cholesterol convert with different factors, so the same sample gives a ratio about 2.3 times smaller in mmol/L. Convert both values to mg/dL first — multiply triglyceride by 88.57 and HDL by 38.67.
Does a high triglyceride to HDL ratio mean insulin resistance?
It is associated with insulin resistance and with a small dense LDL pattern, but it does not diagnose either. Insulin resistance is assessed formally by the euglycaemic clamp, or in practice by HOMA-IR and glycaemic measures.
Why does the ratio perform badly in people of African ancestry?
Because triglyceride concentrations tend to be lower at the same degree of insulin resistance. A markedly insulin-resistant Black patient can have a ratio that appears reassuring, so a low value should not be used to rule the problem out.
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References
- McLaughlin T, Reaven G, Abbasi F, et al. Is there a simple way to identify insulin-resistant individuals at increased risk of cardiovascular disease? Am J Cardiol. 2005;96(3):399–404.
- Sumner AE, Finley KB, Genovese DJ, Criqui MH, Boston RC. Fasting triglyceride and the triglyceride–HDL cholesterol ratio are not markers of insulin resistance in African Americans. Arch Intern Med. 2005;165(12):1395–1400.