What Does Your T Score Really Mean? DEXA Lingo Explained

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Image by Nick Smith photography at bris.ac.uk

Have you, or someone you know had a DEXA (or Ultrasound) test to assess your bone density? If yes I’m going to guess that your results were less than clear. That’s because you were given a T or a Z score, a system that almost requires taking a course to understand!

For good reason, T and Z-scores are not used in other branches of medicine. But for over 20 years they have caused confusion in the realm bone health. So today I will clear it up once and for all…


Bone densitometry (a 1960s advance stemming from nuclear medicine) used to measure bone mineral density of the hip or spine, was initially done in a hospital or clinic. Using X-rays, dual-energy X-ray absorptiometry (DEXA) or by quantitative CT it involved a flatbed full body scanner.

Meanwhile, the sedentary habits and processed nutrient depleted diet of the modern age chipped away at our bone density. So more cost efficient and portable DEXA machines were invented by the 1980s to detect thinning bones – before a painful fracture points it out.

Several different DEXA manufacturers stepped up to get a piece of the pie and provided suitcase sized machines that could quickly and painlessly measure the density of your heel, wrist or fingers. This competition was good for the consumer, because a doctor could make a house call with a small DEXA machine – plus the price was suddenly affordable.

But the problem was that the different DEXA manufacturers couldn’t agree on a standardized measurement. For instance, even though both products said they were reporting grams/cm2, a patient often was about 5-6% higher on a Lunar machine than on a Hologic machine.

If the same measuring standards had been used, then we would always see bone density in gram/cm2, the same way we look at cholesterol simply in mg/dl or weight in kg or lbs.

“T” Is For Truce

A numbering solution was needed to compensate for stubborn manufacturers.
So standardized T Scores, borrowed from the field of statistics, were utilized.

A 50 score, shown as “0.0” on the image below represents the “mean”; the average amongst healthy 25- to 35-year-old adults of your same sex and ethnicity.

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A difference of 10 from the mean indicates a difference of one standard deviation point.
Thus, a score of 70 is two standard deviations above the mean, while a score of 30 is two standard deviations below the mean.

The scoring allows for a certain amount of bone loss as being natural later in life. It’s not assumed that your bone density should be the same as a 25-35 year old, and that’s why a score of -1.0 still falls within ‘normal bone density’ – for a person older than 35 that is.

But if your score goes below -1.0 you get an amber caution sign of ‘osteopenia’…and if it falls to -2.5 or below a full red flag called ‘osteoporosis’ appears letting you know your bone density has fallen too far from what is healthy and normal for your age group.

Z Scores – Keeping Up With The Jones

Your Z-score compares your bone density with that of other people of your age, gender, and race. So as you may be guessing, it’s a less valuable, and potentially deceiving marker.

If you do get a DEXA test, resist the urge to celebrate too much if your Z score comes out as ‘normal’ – because a modern day ‘average’ is typically not something to aspire to.

Our indoor lifestyles, and tempting omnipresent fast, processed foods take a toll on our bone health that is cumulative, rearing it’s porous head much more in older populations than young.

So the average or ‘mean’ bone density of a 50 year old caucasian woman is generally well below what it was in the 1940s. With osteoporosis being declared an epidemic, it is unwise to use the average bone density of elders as a valid measuring stick.


DEXA or Ultrasound tests do not diagnose fractures but they do help to predict your risk of having a bone fracture in the future.

If your T score is -1.0 or lower, you can take certain measures that will increase that number, which will reduce your risk of fracture.

Daily weight bearing exercise and a wholesome diet full of vitamins and minerals is what your body needs to slow bone loss. Despite best intentions, many find it hard to eat the foods they should, and consistently. If this sounds like you, then investing in a high quality calcium supplement is simply affordable health insurance.

If your T score is approaching -2.5 then AlgaeCal Plus and Strontium Boost together can help to reverse extreme bone loss. It is the only formula that is clinically proven to actually increase your bone mineral density.


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Michael Dewey

About Michael Dewey

Mike is AlgaeCal’s Editor in Chief, and was born in Toronto, Ontario. He is responsible for most of AlgaeCal’s writing material such as blog posts, and you might recognize his face from the AlgaeCal newsletters as well. Outside of work, Mike pursues both sporting and creative pursuits. He enjoys beach volleyball, cycling hockey, baseball and snowboarding, but also uses digital technology to compose his own music; merging and stacking layers of instruments and vocals, one-by-one, to make a full band sound.