TyG index

What is TyG index?

Insulin is the hormone that sends glucose into your cells after a meal and tells your liver there is enough. If your cells respond less well to it, which is called insulin resistance, more glucose stays in your blood and your liver, which also misses the signal, makes more triglycerides. Those two consequences can both be measured, fasting, from the same tube, and the TyG index puts them together: the logarithm of your triglycerides times your glucose, divided by two, with both in mg/dL. The index is not a test but a calculation, and no extra tube of blood goes into it. What gives it weight is what it was tested against. It was compared with HOMA-IR, the usual estimate from glucose and insulin, and then with the clamp test, the reference method in which insulin and glucose are given by infusion to measure exactly how sensitive your cells are. The link with that measurement was strong, with a correlation of -0.681, and stayed the same in men and women, with and without excess weight, with and without diabetes. The index appears on no Dutch report; you calculate it from your fasting triglycerides and glucose, after converting to mg/dL, where triglycerides in mmol/L go times 88.6 and glucose times 18. The result has no unit. There is no normal, but there are two boundaries from research: 4.65 against HOMA-IR and 4.68 against the clamp test, both from a Mexican study group. Below that is healthy, and lower is better.

Why is TyG index relevant?

Insulin resistance is the forerunner of type 2 diabetes and precedes a fasting glucose that becomes too high by years, because the pancreas compensates the loss of sensitivity for a long time with more insulin. Anyone who sees it early can reverse it with losing weight, exercise and less sugar. The direct measure, an insulin test, is expensive and in the Netherlands can be drawn at only a handful of places; the TyG index pulls the same pattern out of two numbers you already have. The second reason is that the index shows the gain of lifestyle on two sides. Less sugar and alcohol, losing weight and exercise lower the triglycerides within weeks and the fasting glucose within months, and the index falls on both fronts. In large population studies a higher index is also linked to more cardiovascular disease, fatty liver and kidney damage, also in people without diabetes. The honest limitation is that the index is an approximation and not a diagnosis. The researchers themselves call it a surrogate: it estimates something you would measure with the clamp test and does not replace that measurement. The boundaries come from one study group and were not established in a Dutch population, and the index is only as good as the draw: two non-fasting numbers give an index that measures something else.

TyG index decision limits

No Dutch report prints the TyG index, so there is no band to set beside it. What does exist are two boundaries from the research that introduced and tested the index. They are not interchangeable: the first was calibrated against HOMA-IR, the second against the clamp test, and both come from a Mexican study group, not from a Dutch population. Below 4.65 is healthy, above 4.68 the index fits insulin resistance, and in between the trend says more than the number. Calculate the index only with fasting values.

TyG index high or low: what it means

A low index is favourable and means your cells respond well to insulin. The most common explanation first: a healthy insulin sensitivity, with a healthy weight, little sugar and regular exercise; falling fasting triglycerides, the most mobile of the two input values, which respond within weeks to less sugar and alcohol; and a falling fasting glucose, which follows more slowly. Below 4.65 nothing needs to happen. A high index means your triglycerides and glucose both sit high. Usually it is the first and rarely the last: not drawn fasting, because both glucose and triglycerides rise after a meal and then lift both sides of the sum at once; insulin resistance, what the index was made for, usually through belly fat, little exercise, a lot of sugar and lack of sleep; and rising fasting triglycerides on their own, through alcohol or a lot of fast sugars, even when the glucose is still normal. Above 4.68 the index fits insulin resistance, and then your HbA1c is the next number to set beside it. What you do about it: lose weight if you carry belly fat, because that is the strongest lever, cut soft drinks, fruit juice and sweets, drink less alcohol, and exercise daily, with strength training as well, because muscles are the largest consumer of glucose. Sleep enough. Count on six to twelve weeks before the index shows the change, and then have blood drawn fasting again. With an HbA1c that already sits in the diabetes zone, a treatment plan belongs with it. Read the index beside the fasting triglycerides and glucose themselves, because the same result belongs to several combinations, beside your HbA1c, which shows whether the blood sugar over months is already moving along, beside your HDL, which falls with insulin resistance, and beside your waist size and weight, which usually give away the cause already.

How does a TyG index blood test work?

Referral

Not needed, and there is no separate request. The index follows from your fasting triglycerides and glucose, which you have measured anyway; you calculate it yourself.

Fasting

Yes, for both input values: eight to twelve hours without food, only water, and no alcohol the evening before. An index from non-fasting values measures something else.

When

In the morning, fasting, on an ordinary day with no party the evening before and not during an illness. Six to twelve weeks after a change in diet, weight or exercise to see the effect.

The draw

No extra tube. The index is calculated from the fasting glucose and the fasting triglycerides from the same draw, anywhere you have an ordinary blood test done.

Repeating

Once a year, or six to twelve weeks after a change in lifestyle. This is a value to follow over time, and no extra draw is attached as long as glucose and triglycerides are measured anyway.

Which test

TyG index is in the comprehensive test (€229) and in core.

Where to draw

You can draw at 250+ locations near you, no referral needed. See the locations

Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.