Knowing your Z-score can help you compare your own bone mineral density (BMD) to those of a healthy person of the same age and body size as you, and help predict your risk of bone fractures or osteoporosis. Keep reading to learn about low and high BMD Z-scores, as well as ways to increase it.

What is a Z-Score?

Your Z-score is a comparison of your individual bone mineral density (BMD) to what is expected for a person of the same age and body size as you. The Z-score represents how far off your score is (measured in the number of standard deviations) from the average score of healthy people with similar age, ethnicity, and gender [1, 2].

Z-scores are mainly used in children, premenopausal women, and men under 50 years old instead of T-scores, which compare your BMD to that of a healthy young adult [1, 2].

Normal Range of Z-Score

A normal BMD Z-score ranges from -2.5 to 2.5 [3, 4].

A normal Z-score means that you have a similar BMD to other healthy people in your age group. A lower Z-score means your BMD is lower and a higher Z-score means it’s higher.

Low Z-Score Causes/Associations

A low Z-score is associated with secondary osteoporosis. Osteoporosis is when your bones become weak and brittle, resulting in a higher risk of bone fractures [5, 6].

Unlike primary osteoporosis which is age-related and has unknown causes, secondary osteoporosis is not age-related and results from a specific health disorder or disorders [6].

1) Alcoholism

In a study of 105 people, alcoholic patients had lower Bone Mineral Density (BMD) Z-scores than non-alcoholics. Increased alcohol consumption can also lead to osteoporosis [7].

2) Malnutrition

If you do not get enough vitamins and minerals in your diet, your bones can become weak. Protein and vitamin D deficiency are two common causes of osteoporosis. People with malnutrition generally have lower bone mineral density than people who get enough nutrients from their diet [8, 9, 10].

3) Celiac Disease

Celiac patients have an increased risk of low BMD. In one study, newly diagnosed celiac disease patients had a significantly low Z-score [11].

4) Inflammatory Bowel Disease (IBD)

People with IBD, especially Crohn’s disease, will have low BMD and bone loss. Both ulcerative colitis and Crohn’s disease patients have a decreased BMD Z-score [12, 13].

5) Diabetes

Type 2 diabetic patients have lower bone mineral density compared to healthy patients. Diabetic medications can also reduce BMD. 67 diabetic patients had lower BMD Z-scores compared to healthy people [14].

6) Anorexia

Women with anorexia have lower BMD, impaired bone metabolism, and low BMD Z-scores. Even after patients gain weight, they can still have bone density deficits [15].

7) Liver Disease

Chronic liver disease and liver scarring (cirrhosis) patients have low BMD and Z-scores [16].

8) Cushing Syndrome

Cushing syndrome is a disorder that occurs when your body has too high cortisol levels. High cortisol can cause bone loss, resulting in a lower Z-score [17].

9) Premature Ovarian Failure

Premature ovarian failure, or primary ovarian insufficiency (POI), is the loss of ovarian function before the age of 40. Women with POI have significantly lower BMD and Z-scores than healthy women [18].

10) Thyroid Conditions

Both hyperthyroidism (overactive thyroid glands) and hypothyroidism (underactive thyroid glands) are associated with osteoporosis and increased bone fracture risk. Patients with toxic goiters (which eventually leads to hyperthyroidism) have low BMD Z-scores [19, 20].

11) Hyperparathyroidism

Overproduction of parathyroid hormone from the parathyroid glands (hyperparathyroidism) increases bone fracture risk. In one study (n=216), the patients had bone loss and significantly decreased BMD Z-scores [21].  

12) Multiple Myeloma

Multiple myeloma is a cause of secondary osteoporosis; patients have lower BMD and BMD Z-scores compared to healthy people. After treatment for myeloma, their BMD dramatically increases [22].

13) Drugs

The following drugs can cause secondary osteoporosis and are associated with low BMD Z-scores [5, 19, 23]:

  • Steroids
  • Antiepileptic drugs
  • Antidepressants
  • Proton pump inhibitors
  • Anticoagulants (blood thinners)

Ways to Increase Your Z-Score


Eat more fruit and vegetables. In two studies (n=926, n=3089), fruit and vegetable intake was associated with increased BMD and BMD Z-score. Elderly people also had a reduced risk of osteoporosis [24, 25].  

Consume more calcium, which is essential for healthy bones. In a study of 4,797 adults, milk consumption was associated with higher BMD and BMD Z-score [26].

Limit your caffeine intake. Drinking a lot of coffee (about four or more cups per day) can increase the risk of bone fracture. Caffeine promotes calcium excretion in the urine, which negatively impacts your calcium balance [27, 28].

Get enough protein, but not too much. Protein is required for healthy bones, but as your body digests protein, it releases acids into the bloodstream, which the body neutralizes by drawing calcium from the bones. Over time, this can result in weaker bones [29].

Lifestyle Changes

Refrain from drinking too much alcohol. In a study of 105 people, alcohol consumption was associated with bone loss, breakdown, and low BMD Z-scores. When they stopped drinking alcohol, vitamin D and osteocalcin levels increased, indicating an increase in bone mass and BMD [7].


1) Vitamin D

Vitamin D supplementation can help increase BMD and Z-scores, but only in patients with vitamin D deficiency [9, 30].

2) Calcium

Similarly, calcium supplementation only increases BMD and Z-scores in calcium-deficient patients [31, 30],

3) Vitamin K2

Vitamin K2 supplementation increases BMD [32, 33].

4) Magnesium and Potassium

Magnesium and potassium supplementation increases BMD and reduces the risk of bone fractures [32, 34].

5) Fish Oil

In various studies, fish oil increased calcium absorption and bone formation [35],

High Z-Scores

A high BMD Z-score indicates that you have a high bone mineral density. A high BMD is not a good indicator of bone health, because a person’s BMD may be elevated in certain conditions [4].

Causes of High Z-Scores

The following conditions result in a high BMD [4]:

  • Fractured vertebrae  
  • Spondylosis (spinal disk degeneration)
  • Fluorosis (white lines or streaks on the teeth caused by overexposure to fluoride)
  • Sclerosteosis (a genetic disorder that causes bone overgrowth)
  • Diffuse idiopathic skeletal hyperostosis (hardening of ligaments in areas that attach to the spine)
  • Ankylosing spondylitis (inflammatory disease that affects the spine and large joints)
  • Paget’s disease (a bone disorder that disrupts the replacement of old bone tissue with new bone tissue)
  • Myelofibrosis (bone marrow disorder)
  • Acromegaly (overproduction of growth hormones)
  • Renal osteodystrophy (a disease with abnormal levels of calcium and phosphorous in the kidneys)
  • Tuberous sclerosis (the growth of many non-cancerous tumors in the skin, brain, lungs, heart, and other organs)
  • Tumors

You should get medical attention for any underlying health conditions.

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