Vitamin D deficiency: 6 symptoms you should not ignore: A clinical evidence review
What vitamin D deficiency means
Vitamin D is a fat-soluble nutrient that helps the body absorb calcium and phosphate, supporting bones and teeth. It also contributes to normal muscle function, nerve signaling and immune processes. The body can produce vitamin D after sunlight exposure, while dietary sources include oily fish, egg yolks, fortified dairy products and fortified plant-based alternatives. A 2025 analysis reported that more than 20% of U.S. adults were at risk of vitamin D insufficiency or deficiency. 1
Low vitamin D does not always produce noticeable symptoms. In many people, signs appear only after a severe or prolonged deficiency, and common complaints can overlap with sleep problems, other illnesses, medication effects or normal aging. A blood test measuring 25-hydroxyvitamin D is the reliable way to confirm deficiency, rather than using symptoms alone as a diagnosis. 2
Six symptoms that warrant attention
The six symptoms below are associated with low vitamin D, but none is specific enough to prove a deficiency. Their significance increases when they persist, occur together, or appear in someone with limited sunlight exposure, a condition affecting nutrient absorption or another recognized risk factor. Severe symptoms, unexplained fractures or worsening weakness require medical assessment because other causes may need treatment. 3
| Symptom | What it may look like |
|---|---|
| 1. Persistent fatigue | Low energy despite adequate rest, without an obvious explanation. |
| 2. Bone pain | Deep or widespread discomfort, including lower-back, hip, rib or leg pain. |
| 3. Muscle weakness or cramps | Difficulty climbing stairs, rising from a chair, carrying groceries or walking normally. |
| 4. Fragile bones or fractures | Broken bones after relatively minor impacts, reflecting impaired mineralization. |
| 5. Low mood | Depressive symptoms or mood changes associated with low vitamin D levels. |
| 6. Frequent illness or slow recovery | Repeated infections or recovery that seems slower than expected. |
Fatigue and changes in physical strength
Persistent tiredness is frequently reported in discussions of vitamin D deficiency, including exhaustion that does not improve after sufficient sleep. However, fatigue also occurs with anemia, thyroid disorders, sleep apnea, infection, depression and many other conditions. It should therefore be treated as a reason to review overall health, not as evidence that vitamin D is the sole cause. 4
Muscle weakness, aches or cramps may be more functionally important than general tiredness. A person may notice difficulty climbing stairs, standing from a seated position, exercising at a previous level or maintaining balance. Severe deficiency can contribute to neuromuscular problems and falls, particularly among older adults. New or progressive weakness deserves clinical evaluation regardless of whether vitamin D status is eventually found to be low. 3
Bone pain and fracture risk
Vitamin D supports calcium absorption and normal bone mineralization. When deficiency is severe and prolonged, adults can develop osteomalacia, a condition involving softened or weakened bones. Symptoms may include throbbing or deep bone discomfort in the lower back, hips, ribs or legs, as well as muscle weakness and walking difficulty. These symptoms can be mistaken for arthritis, posture-related strain or ordinary aging. 5
Unusually fragile bones or fractures after limited trauma are among the more serious warning signs. Prolonged deficiency can weaken the skeleton and increase fracture risk, although osteoporosis, falls, medications and other metabolic disorders can also contribute. Bone pain or a fracture should not be managed solely with supplements because determining the underlying cause may require examination, blood testing and assessment of bone health. 6
Mood, immunity and symptoms that overlap
Low mood and depressive symptoms have been associated with low vitamin D levels, and mood changes are listed among possible manifestations of deficiency. The relationship is not proof of causation: depression has numerous biological, psychological and social contributors. Persistent sadness, loss of interest, hopelessness or thoughts of self-harm require appropriate mental-health support independently of any vitamin test result. 4
Vitamin D participates in immune-system functions, so frequent colds, repeated infections or slow recovery are sometimes discussed as possible signs of low levels. Evidence does not make recurrent illness a specific diagnostic symptom, since exposure, age, chronic disease, sleep and immune disorders also matter. Repeated or unusually severe infections should be discussed with a clinician rather than attributed automatically to vitamin D deficiency. 7
Who has a higher risk of deficiency
Risk is higher when skin receives little ultraviolet exposure, including among people who spend most of their time indoors or are homebound. People with darker skin may produce less vitamin D from the same sunlight exposure. Older age, obesity and diets lacking vitamin-D-containing or fortified foods are also recognized risk factors. Geographic location, season and clothing can further affect sunlight-related production. 7
Digestive conditions such as celiac disease and Crohn's disease can interfere with absorption, while chronic kidney or liver disease can affect vitamin D metabolism. Some medicines, including certain anti-seizure drugs, may increase vitamin D breakdown. These factors matter because a symptom-based approach can miss deficiency in people who have no obvious complaints, while risk alone does not confirm a diagnosis. 2
Testing, treatment and safety considerations
A healthcare professional can decide whether a 25-hydroxyvitamin D blood test is appropriate and interpret the result alongside age, medical history, medications and symptoms. Testing is particularly relevant when bone pain, muscle weakness, unexplained fractures or significant risk factors are present. Reported thresholds can vary by laboratory and guideline, so results should not be interpreted from an isolated online range. 2
Treatment commonly involves vitamin D supplementation and addressing contributing factors under medical guidance, with dietary sources and appropriate sunlight exposure considered as part of the overall plan. High-dose self-treatment is not risk-free because excessive vitamin D can cause hypercalcemia and kidney or other health problems. Children require particular attention because severe deficiency can cause rickets, poor growth, delayed motor development, bone pain and skeletal deformities. 8
Sources
- UPMC HealthBeat, What Are the Signs of Low Vitamin D?
- Acibadem Hospitals Group, Low Vitamin D: 7 Signs And When To See A Doctor
- National Institutes of Health Office of Dietary Supplements, Vitamin D Health Professional Fact Sheet
- NHS, Vitamin D
- Verywell Health, 3 Signs You May Be Low on Vitamin D
- Cleveland Clinic, Vitamin D Deficiency
- Healthdirect Australia, Vitamin D
- Royal Children's Hospital Melbourne, Vitamin D Deficiency Clinical Guideline