A bone density test, also known as bone densitometry, is a specialized medical scan used to measure the mineral content and density of your bones. The gold-standard technique for this measurement is called Dual-Energy X-ray Absorptiometry, commonly referred to as a DEXA or DXA scan. This test is a crucial tool for diagnosing osteoporosis, a condition that causes bones to become weak, brittle, and more susceptible to fractures.

Osteoporosis is often called a "silent disease" because it progresses without any symptoms until a fracture occurs. The DEXA scan allows for the early detection of low bone mass, enabling your doctor to assess your risk of a future fracture and recommend preventive measures or treatment long before a serious injury happens. The procedure is quick, completely painless, and involves a very low dose of radiation, making it an exceptionally safe and effective screening method. It provides a clear, quantitative measure of your bone health, which is then compared to the bone density of a healthy young adult to generate a "T-score." This score helps to categorize your bone health as normal, having low bone mass (osteopenia), or having osteoporosis.

For millions of individuals, especially postmenopausal women and older men, the bone density test is a vital component of proactive healthcare, offering the essential information needed to protect bone strength, maintain mobility, and ensure a healthy, active future.

What is a Bone Density Test (DEXA Scan)?

A DEXA scan is the most widely used and most accurate method for measuring Bone Mineral Density (BMD). It is a type of medical imaging that uses two different, low-energy X-ray beams. One beam is primarily absorbed by soft tissue, while the other is absorbed by bone. By measuring the differential absorption of these two beams as they pass through your body, the DEXA machine can subtract the density of the soft tissue and calculate a highly precise measurement of the mineral content of your bones.

Unlike a standard X-ray, which can only detect osteoporosis after significant bone loss (often 30-40%) has already occurred, a DEXA scan can detect very small changes in bone density, making it the ideal tool for early diagnosis. The procedure typically focuses on measuring the bone density in two key areas that are most prone to osteoporotic fractures:

• The Lumbar Spine: The vertebrae of the lower back.
• The Hip: Specifically, the femoral neck, which is a common site for debilitating hip fractures.

In some cases, the scan may also include the forearm (wrist), especially if hip or spine measurements are not possible. The test provides a clear, objective measure of your current bone mass, which is a primary determinant of your bone's strength and its ability to withstand stress and trauma.

The Science: Understanding Bone Health and Osteoporosis

To understand why a bone density test is so important, it is crucial to understand that bone is a living, dynamic tissue that is in a constant state of renewal.

The Bone Remodeling Cycle

Throughout your life, your skeleton is constantly being remodeled in a process involving two specialized types of bone cells:

• Osteoclasts: These are cells responsible for "resorption," the process of breaking down and removing old, damaged bone tissue.
• Osteoblasts: These are the "bone-building" cells that follow the osteoclasts, laying down new, strong bone matrix to replace what was removed.

In childhood and young adulthood, bone formation by osteoblasts outpaces bone resorption by osteoclasts, leading to an increase in bone size and density. We achieve our Peak Bone Mass; the strongest and densest our bones will ever be; in our late 20s. After this point, the remodeling process remains relatively balanced for several years. However, as we age, the rate of bone resorption gradually begins to exceed the rate of bone formation, leading to a slow, progressive loss of bone mass.

What is Osteoporosis?

Osteoporosis, which literally means "porous bone," is a disease that occurs when the loss of bone mass becomes excessive, or when the body makes too little new bone, or both. The internal honeycomb-like structure of the bone becomes more porous, and the outer shell becomes thinner. This compromises the bone's architectural integrity, making it weak, fragile, and highly susceptible to fracture from a minor fall, a bump, or even a sneeze; a type of injury known as a fragility fracture.

The most dangerous consequence of osteoporosis is a hip fracture, which can lead to a loss of independence, chronic pain, and an increased risk of mortality. The primary driver of accelerated bone loss in women is menopause. The hormone estrogen plays a critical protective role in bone health by slowing down the activity of osteoclasts. When estrogen levels plummet during menopause, the osteoclasts become overactive, leading to a rapid and significant decrease in bone density.

When is a Bone Density Test Recommended?

A DEXA scan is a screening tool recommended for individuals who are at risk for osteoporosis. You should talk to your doctor about getting a bone density test if you are:

• A woman age 65 or older.
• A postmenopausal woman under age 65 with one or more risk factors.
• A man age 70 or older.
• A man under age 70 with risk factors.
• Anyone who has experienced a fracture after the age of 50.
• An individual with a medical condition associated with bone loss, such as rheumatoid arthritis or thyroid disorders.
• Someone taking long-term steroid medications (like prednisone), which can cause significant bone loss.
• An individual being treated for osteoporosis, to monitor the effectiveness of the treatment.

Key Risk Factors for Osteoporosis:

• Non-Modifiable: Female gender, advancing age, postmenopausal status, a family history of osteoporosis, a small and thin body frame.
• Modifiable & Medical: Low lifetime intake of calcium and vitamin D, a sedentary lifestyle, smoking, excessive alcohol consumption, eating disorders, and certain endocrine disorders.

Interpreting Your DEXA Scan Results: T-scores and Z-scores

The results of your DEXA scan are reported using two main scores.

The T-score

This is the most important score for diagnosing osteoporosis in postmenopausal women and men over the age of 50. The T-score compares your Bone Mineral Density (BMD) to the average peak bone mass of a healthy 30-year-old of the same sex. It is measured in units of standard deviations (SD).

A diagnosis of osteopenia means your bone density is lower than normal but not yet low enough to be classified as osteoporosis. It is a critical warning sign that you are at an increased risk of developing osteoporosis in the future.

The Z-score

The Z-score compares your BMD to the average BMD of a person of your same age, sex, and ethnicity. The Z-score is not used to diagnose osteoporosis in older adults but is the preferred score for evaluating bone density in premenopausal women, men under 50, and children. A very low Z-score (below -2.0) may suggest that there is an underlying medical cause for the low bone density beyond normal aging.

Our Specialists

The management of bone health and osteoporosis is often a collaborative effort involving specialists in endocrinology, rheumatology, orthopedics, and internal medicine.

Dr. R Muralidharan

DIRECTOR ENDOCRINOLOGY | Fortis Mohali

Dr. Kaushik Bhojani

DIRECTOR RHEUMATOLOGY | Fortis Mulund

Patient Stories

“I had my first DEXA scan when I turned 65, as my doctor recommended it as a routine screening. I was surprised when the results showed I had osteopenia. I had no symptoms and felt perfectly healthy. My endocrinologist explained that this was my window of opportunity to be proactive. We created a plan that included increasing my calcium and vitamin D intake and starting a new regimen of weight-bearing exercises. My follow-up scan two years later showed that my bone density had stabilized. That simple test empowered me to take action to prevent a future fracture”.  — S. Mehra, 67, Delhi

“After I slipped and fractured my wrist from a simple fall, my orthopedic surgeon insisted I get a DEXA scan. The result confirmed I had significant osteoporosis. It was frightening to learn how fragile my bones had become without me even knowing. My doctor started me on a treatment plan with medication and a focus on fall prevention. The DEXA scan was a critical diagnostic step that explained why I had fractured so easily and put me on the path to building stronger, safer bones for the future.”  — P. Khanna, 72, Gurugram

The Bone Density Test Procedure: A Detailed Walkthrough

The DEXA scan is one of the easiest and most comfortable medical tests you can have.

Preparation for the Test

• You can eat and drink normally on the day of the test.
• You should not take calcium supplements for at least 24 hours before your scan.
• Wear loose, comfortable clothing without any metal zippers, belts, or buttons. You may be asked to change into a hospital gown.
• Inform the technician if you have recently had a barium study or a CT scan with contrast dye, as this can interfere with the results. You will also need to inform them if there is any possibility that you are pregnant.

What Happens During the Test

• Positioning: You will be asked to lie down on a padded table. The DEXA scanner has a large scanning arm that will pass over your body.
• The Scan: You will need to remain still as the scanner moves over your lower spine and hip. The arm of the scanner passes several feet above you; it does not touch you. The process is completely painless.
• Duration: The entire procedure is very quick, typically taking only 10 to 20 minutes to complete.

After the Test: Next Steps and Management

The results from your DEXA scan will be analyzed by a radiologist and sent to your doctor. Your doctor will then discuss the findings with you and recommend a management plan based on your T-score and your overall fracture risk.

• If your bone density is normal: The focus will be on preventive lifestyle measures, including adequate calcium and vitamin D intake and regular weight-bearing exercise.
• If you have osteopenia: Your doctor will strongly recommend lifestyle changes to prevent further bone loss. Depending on your T-score and other risk factors, they may also discuss starting a medication to protect your bones.
• If you have osteoporosis: Your doctor will prescribe a medication specifically designed to treat osteoporosis. These medications work by either slowing down bone resorption or stimulating new bone formation. This will be combined with a comprehensive plan for calcium, vitamin D, and safe exercises.

Myths vs Facts

Take the Next Step

Protecting your bone health is a critical investment in your long-term independence and quality of life. A fragility fracture can be a life-altering event, but the good news is that osteoporosis is a detectable and treatable condition. A bone density test is the first and most important step in understanding your risk.

It is a simple, painless scan that provides powerful information, empowering you and your doctor to take proactive steps to keep your bones strong and resilient for years to come. If you are in an at-risk group, speak with your doctor about scheduling your DEXA scan.

CTA: Book a Health Check / Consult an Endocrinologist

Frequently Asked Questions

1. Is the bone density test painful?

Ans. No, the procedure is completely painless and non-invasive. You simply lie still on a comfortable table while the scanner passes over you.

2. How long does it take to get the results?

Ans. The images are available immediately, but a specialist radiologist needs to analyze the data and prepare a formal report. This report is typically sent to your referring doctor within one to two business days.

3. What is the difference between a DEXA scan and a regular X-ray?

Ans. A regular X-ray is excellent for showing fractures and the shape of bones, but it is not sensitive enough to measure bone density. A DEXA scan uses a specialized dual-energy technique that is specifically designed to provide a highly accurate, quantitative measurement of bone mineral content.

4. How often should I have a bone density test?

Ans. The frequency depends on your initial results and risk factors. If your first test is normal, you may not need another one for several years. If you have osteopenia or are being treated for osteoporosis, your doctor will likely recommend a follow-up scan every one to two years to monitor for changes.

5. What is the FRAX score?

Ans. The FRAX tool is a fracture risk assessment calculator developed by the WHO. Your doctor will often use your DEXA scan result along with other risk factors (like your age, weight, and history of smoking) to calculate your 10-year probability of having a major osteoporotic fracture. This helps in making treatment decisions, especially for patients with osteopenia.

6. Is a DEXA scan the same as a bone scan?

Ans. No, they are very different tests. A DEXA scan measures bone density to check for osteoporosis. A nuclear medicine bone scan is a more complex imaging test that involves injecting a radioactive tracer to detect cancer, fractures, or infections in the bone.

7. Can men get osteoporosis?

Ans. Yes. Although it is more common in women, men can and do get osteoporosis. Risk factors for men include low testosterone levels, long-term steroid use, smoking, and excessive alcohol intake.

8. What are "weight-bearing" exercises?

Ans. These are exercises where your bones and muscles work against gravity to support your body's weight. Examples include walking, jogging, climbing stairs, dancing, and strength training with weights. These activities stimulate osteoblasts to build stronger bones.