Vitamin D Deficiency Symptoms: Signs, Causes and Testing
Mild vitamin D deficiency usually has no obvious symptoms. When symptoms appear, the most typical are bone pain, muscle weakness or aches, and fatigue. Severe, long-lasting deficiency causes rickets in children and osteomalacia (soft bones) in adults. The only reliable way to know is a 25-hydroxyvitamin D blood test.
Vitamin D deficiency is common, yet many people with it feel completely fine. That's what makes vitamin D deficiency symptoms tricky: by the time they're noticeable, levels have often been low for a long time.
Common symptoms
When low vitamin D does cause symptoms, they tend to involve bones and muscles:
- Bone pain or tenderness, often in the lower back, hips, legs or ribs
- Muscle weakness, especially in the thighs and upper arms, making stairs or standing up harder
- Muscle aches and cramps
- Fatigue
- Frequent falls in older adults, partly because of muscle weakness
In children
Severe deficiency causes rickets: soft, weak bones that lead to bowed legs, delayed growth, dental problems and skeletal deformities.
In adults
Long-term deficiency causes osteomalacia (softening of the bones) and contributes to osteoporosis, raising the risk of fractures.
What blood levels mean
Doctors measure 25-hydroxyvitamin D (25(OH)D):
| Level | Interpretation |
|---|---|
| Below 12 ng/mL (30 nmol/L) | Deficient |
| 12–20 ng/mL (30–50 nmol/L) | Possibly inadequate |
| 20 ng/mL (50 nmol/L) or higher | Adequate for most people |
Some labs and specialist groups use higher cut-offs, so ask how your result was interpreted.
Who is most at risk
- Little sun exposure: indoor workers, people who cover most of their skin, long winters at higher latitudes
- Darker skin, which makes less vitamin D from the same sun
- Adults over 65, whose skin produces less vitamin D
- Obesity, as vitamin D is held in fat tissue
- Breastfed infants without a vitamin D supplement
- Digestive conditions that reduce fat absorption, such as Crohn's disease, celiac disease or weight-loss surgery
- Kidney or liver disease, which affect how vitamin D is activated
- Certain medications, including some anti-seizure drugs, glucocorticoids and orlistat
Getting tested
If you have symptoms or several risk factors, ask your doctor about a 25(OH)D test. Routine screening of healthy adults without risk factors isn't generally recommended.
How deficiency is treated
Treatment depends on how low you are. A doctor may prescribe a higher daily or weekly dose for a period, then a maintenance dose. Don't self-prescribe very high doses; vitamin D can build up to harmful levels. Read how much vitamin D is too much to understand the limits.
For prevention, most adults do well with 600–2,000 IU a day, taken with a meal that contains fat. See the best time to take vitamin D.
The bottom line
Vitamin D deficiency symptoms are often absent or vague: bone pain, muscle weakness and tiredness are the most typical. If you're in a higher-risk group or have these symptoms, a simple blood test gives a clear answer and guides the right dose. More on what vitamin D does is in our vitamin D3 guide.
Frequently asked questions
Can low vitamin D cause tiredness?
It can contribute, and fatigue is commonly reported. But tiredness has many causes, including low iron, thyroid problems and poor sleep, so test rather than assume.
Does low vitamin D cause hair loss?
Some studies link low vitamin D with certain types of hair loss, but it isn't established that supplements regrow hair in people who aren't deficient.
How long does it take to fix low vitamin D?
Blood levels usually rise over 2–3 months of daily supplementation. Your doctor will choose the dose based on how low you are and may recheck your level.
Sources
This page is for education and is not a substitute for advice from your doctor. Read our medical disclaimer.