Your bone density T-score and what to do about it

A T-score of -1.0 or higher is normal. Between -1.0 and -2.5 is osteopenia. Minus 2.5 or lower is osteoporosis. That's the entire grading system, set by the World Health Organization decades ago, and it's the reason a one-page printout can rearrange how you think about the next twenty years of your life.

The score isn't a percentage and it isn't a grade out of ten. It's standard deviations away from the average bone mineral density of a healthy young adult at peak bone mass. So -2.0 means you're two standard deviations below a 30-year-old in their prime. Every step of 1.0 down the scale roughly doubles fracture risk, which is why the difference between -1.4 and -2.6 isn't a rounding error.

The scan itself takes ten minutes and you keep your clothes on

DEXA stands for dual-energy X-ray absorptiometry. You lie on a padded table, a scanning arm passes over your lower spine and one hip, and a tech tells you to hold still and breathe normally. Radiation dose is very low, well under a chest X-ray. No needle, no contrast dye, no fasting.

Three things go wrong at this appointment and all three are avoidable.

• Don't take calcium supplements for 24 hours beforehand. Undissolved tablets in your gut can throw off the spine reading.
• Wear sweatpants and a plain shirt. Zippers, snaps, belt buckles and underwire all confuse the image, and you'll end up in a gown anyway.
• Ask which machine you were scanned on, and go back to that one. Different manufacturers calibrate differently. A follow-up scan at a different clinic can't be compared to your first one with any confidence, and nobody tells you this until you've already wasted two years of data.

One more piece of confusion worth clearing up. The body composition DEXA you paid $75 for at a strip-mall gym to find out your body fat percentage is the same technology pointed at a different question. It's not a bone density report. If you want the T-score, you need the clinical scan of the hip and spine, ordered by a doctor and read by a radiologist.

Write down four numbers, not one

The report will list a T-score for lumbar spine, femoral neck and total hip. The lowest of those is the one that classifies you. A great spine score doesn't cancel out a bad hip.

Also find the raw bone mineral density in grams per square centimeter. The T-score gets recalculated against reference databases that occasionally change; the BMD is the actual measurement. Five years from now, the g/cm² comparison is what tells you whether you're holding, gaining or sliding.

Then look for the Z-score. That compares you to people your own age and sex, not to a 30-year-old. For men over 50 and women past menopause, the T-score is what counts. Under 50, and for premenopausal women, the Z-score is the meaningful one, and a Z-score at or below -2.0 is a flag that something specific is going on rather than ordinary aging.

Which brings up the part that gets skipped.

Osteopenia isn't a diagnosis, it's a homework assignment

Most people who get a DEXA land in that -1.0 to -2.5 band. The visit ends with "a little thinning, nothing to worry about yet, we'll recheck in a few years," and then five years evaporate and the second scan is worse. That's the standard story, and it's mostly a failure of follow-up rather than a failure of medicine.

Two questions to ask before you leave the room.

First: what's my FRAX score? FRAX is a free calculator that combines your femoral neck BMD with age, sex, weight, height, prior fractures, parental hip fracture, smoking, steroid use, rheumatoid arthritis and alcohol intake to estimate your ten-year probability of a major fracture. It's a better decision tool than the T-score alone. Two people can both sit at -2.1 and have very different risk, and FRAX is where that shows up.

Second: is there a secondary cause? Low bone density in a 45-year-old who lifts isn't a normal finding. Doctors typically look at calcium, vitamin D, kidney and thyroid function, parathyroid hormone, celiac markers, and in men, testosterone. Long-term steroid use, certain anti-seizure drugs, years of proton pump inhibitors, heavy drinking and smoking all show up in bone. So does a long history of eating too little for how much you train. A cause you can fix is worth more than any supplement.

Whether medication makes sense is a conversation for your doctor, and for some people at -2.5 or below with fracture history it clearly does. That's not a call anybody makes from an article.

The training part, for people who have jobs and kids

Bone responds to two things: heavy load and impact. It doesn't respond meaningfully to walking, cycling or swimming, which are fine for your heart and nearly useless for your femoral neck. Swimmers famously have unremarkable bone density. Water doesn't push back hard enough.

What works is progressive resistance training, two or three sessions a week, on movements that load the hip and spine directly. Squat variations. Deadlift or trap-bar deadlift. Overhead press. Loaded carries. Weighted step-ups, which hit one hip at a time and are kinder to a cranky back than barbell squats.

Heavy means heavy. A weight you could lift 20 times is a conditioning exercise; sets of 5 to 8 near real effort are what registers as a signal. Build to that over months, not weeks, and ask a physical therapist to watch your setup if you've got any fracture history at all.

Add impact if your joints tolerate it. Twenty to thirty hops, jumps or drop-landings, a few days a week, takes two minutes and has a track record for hip density. Do them at the start of a session when you're fresh, not at the end when you're sloppy.

If you've already got osteoporosis or a vertebral fracture, the standard caution is to avoid loaded forward bending and hard twisting under load. That means no sit-ups, no weighted crunches, no toe-touch stretches with a dumbbell. Hinge from the hips with a neutral spine instead.

The other half of fracture prevention isn't falling

You don't break a hip because of a number. You break it because you hit the floor. So train the thing that keeps you off the floor: single-leg balance while you brush your teeth, step-downs from a low box, carrying something in one hand on uneven ground. Two minutes a day, free, and it works.

Then go through the house like an insurance adjuster. The throw rug at the top of the stairs. The extension cord across the hallway. The bathroom with nothing to grab. The dark landing with the burned-out bulb you've been ignoring since March.

Food, briefly, without the supplement aisle

Standard guidance for adults sits around 1,000 to 1,200 mg of calcium a day and 800 to 1,000 IU of vitamin D, and food beats pills for the calcium half. A cup of plain yogurt, a glass of milk, a can of sardines with the bones, a cup of cooked greens. Get enough total protein and enough total calories, because bone is a living tissue and it doesn't build on a deficit. If you've got kidney stones or kidney disease, ask before you add calcium.

None of this is medical advice, and your doctor gets the final word on your report.

Bone is the tissue that only improves when you give it a reason to worry. Twice a week, something heavy, and thirty hops. That's the reason.