What's osteopenia, or low bone density?

“Osteopenia” is not a word I’d ever heard three months ago. And then, just like that, it was everywhere—on the results of my first bone-density, or DEXA, scan, and on the lips of most of the friends of a certain age who, when I mentioned the diagnosis, responded with, “I have that, too!”

Turns out that low bone density, by which osteopenia is interchangeably referred, is pretty common: An estimated 40 million Americans have the condition, with about one-third of adults older than 50 having some degree of bone density loss.

What is osteopenia, or low bone density?

It is a step below—and what sometimes precedes—osteoporosis, which causes bones to become weak, brittle, and more prone to fractures. It occurs when bone, which is a living tissue that is constantly lost and replaced, is only lost, without the rate of replacement able to keep up.

So how worried should people with the diagnosis be? And is there any way to halt or reverse it? Read on for everything you need to know about osteopenia.

Low bone density, explained

Osteopenia is asymptomatic, so it takes a bone-mineral density test—which determines your bone density, as higher mineral concentration makes bones more dense—to know if you’ve got it. The test is done through the super quick and painless DEXA scan, which uses radiation to measure how much calcium and other minerals are present.

Results for patients over 50 come in the form of a T-score, which is the difference between your bone mineral density and 0—the bone mineral density of a healthy young adult. The lower your T-score, the higher your risk of bone fracture. So if your score is:

1 or higher, your bones are healthy.
1 to –2.5, you have osteopenia, or low bone mineral density.
2.5 or lower, you might have osteoporosis.

The risk of broken bones increases by 1.5 to 2 times with each 1-point drop in the T-score.

But it’s a continuum, and no single T-score gives the whole story, says Dr. Andrea Singer, chief medical officer of the Bone Health and Osteoporosis Foundation and a Georgetown University Hospital internist specializing in bone health.

“There’s no absolute number or cut-off that guarantees somebody will fracture, although we know that the lower the bone density, the greater the risk for fracture,” Singer tells Fortune. “There’s also no bone density that renders somebody safe from fracture. The better the bone density, generally, the lower the fracture risk. But there are many other things that come into play in addition to bone density.”

You’ve been told you have osteopenia. Now what?

“What one would suggest we do about it really depends on not only looking at the bone density, but looking at the individual patient and what other risk factors they may have,” Singer says, explaining that such individual factors are used to assess one’s overall risk for fracture, often done through a FRAX score, which is based on various lifestyle factors and the T-score.

“The reason we care about these numbers, and the reason we treat people who are at high risk, is to prevent fractures, which can be life altering events,” she explains. “Our goal is to keep people independent, mobile, doing all of the things we want to do. And with most diseases, it’s easier to prevent things than to try to reverse things.”

Risk factors to take into account when being assessed for bone-loss treatment, according to the Cleveland Clinic, include:

A recently broken bone
Being over 50
Being a woman—especially if you’re postmenopausal.
If you have a family history of osteoporosis
If you are prone to falls
If you are naturally thin or have a smaller frame
Being a smoker or user of tobacco products
Having an endocrine disorder, gastrointestinal disease, or autoimmune or blood disorder
If you take certain medications, including diuretics, corticosteroids, and hormone therapy for cancer
If you are deficient in vitamin D, don’t get enough exercise, or drink alcohol regularly

There is no one physician specialty that “owns” osteopenia or osteoporosis, Singer says, and is something that could be treated by a primary care physician, internist, family medicine practitioner, OB/GYN, endocrinologist, rheumatologist, and some orthopedists.

Whichever doctor you choose, sit down with them and go over your test results, medical history and family history, she suggests, as there is “no one-size-fits-all” approach to treatment. The many options, depending on one’s individual needs, range from lifestyle changes to medications, and include:

Physical activity, especially weight-bearing exercises that put stress on bones, thereby helping to build and maintain density
Vitamin and mineral supplements, especially calcium and vitamin D
A healthy eating plan including foods with vitamins and minerals to strengthen bones such as dairy and green, leafy vegetables; working with a nutritionist can help with the plan
Prescribed medications, especially if you’ve already broken a bone. Options include bisphosphonates (such as Fosomax or Actonel), which slow the body’s natural process of bone loss; hormone replacement therapy; Teriparatide, which, taken as a shot beneath the skin, mimics a hormone that helps you make new bone tissue; and Raloxifene, which is a daily pill.

It’s never too early to worry about bone health

“We should be thinking about bone health in childhood and even the teen years,” says Singer, “because that’s when people accrue most of their bone and reach a peak bone density.”

About 90% of bone density is accrued by one’s early 20s, with peak bone density, for most, coming around the age of 30.

The best way to not lose that mineral-rich density, she says, is by making sure kids and adolescents are eating a healthy diet, staying active, and not smoking or drinking—all of which of course bring benefits beyond bone density, from heart health to cancer prevention.

Into adulthood, Singer adds, “It’s important for people to pay attention and make sure that they have a well balanced diet,” including adequate calcium and vitamin D as well as protein for muscle strength.

“At every stage along the way, it’s important—but especially as we’re approaching menopause and that menopausal transition—to kind of know where you are and take stock of things,” she says. “It means, at the very least, discussing your risk factors with your clinician.”