What are symptoms of too little vitamin D?

Vitamin D is essential for bone health, immune function, muscle strength and aspects of mental well-being. When levels fall below recommended ranges, a variety of signs can emerge. This article summarizes common and subtle symptoms of insufficient vitamin D, explains likely causes and outlines how deficiency is generally confirmed.

Common symptoms to recognize

Symptoms of too little vitamin D often develop gradually and can be nonspecific. Frequently reported complaints include persistent fatigue that does not improve with rest, general muscle weakness, and diffuse bone pain, especially in the hip, lower back or ribs. Individuals may also experience slower recovery from injuries and delayed wound healing.

Low vitamin D has been associated with increased susceptibility to upper respiratory infections and other frequent illnesses, reflecting its role in immune regulation. Mood changes such as low mood or greater irritability and episodes of seasonal worsening are also commonly noted in observational studies. Less commonly, hair thinning and impaired cognitive clarity or “brain fog” have been reported.

Subtle signs often missed

Some indicators are easy to overlook: mild, persistent muscle soreness after light exertion, uncharacteristic tiredness during routine activities, and small but ongoing bone discomfort that may be misattributed to aging or overuse. In children, deficiency can present as growth delay, skeletal deformities, or irritability; in older adults, even modest deficiencies can increase fall and fracture risk.

Why levels become low

Common causes include inadequate sun exposure, higher skin melanin content, aging skin, dietary insufficiency, certain gastrointestinal malabsorption conditions, obesity (which can sequester vitamin D in adipose tissue), and some medications that alter vitamin D metabolism. Lifestyle and geographic factors together explain why deficiency remains common despite broad awareness of the vitamin’s importance.

Confirming deficiency

Diagnosis is typically based on a blood test measuring 25-hydroxyvitamin D (25[OH]D). Most clinical guidelines consider levels below 20 ng/mL deficient and 20–30 ng/mL insufficient, although targets may vary by region and individual circumstances. Healthcare providers often combine test results with symptom history and risk factors to guide intervention and monitoring.

Further reading and resources

For more detail on common signs and diagnostic thresholds, see this overview of the symptoms of too little vitamin D. Information about when multivitamin use may be advisable is discussed in a complementary piece on when it may be advisable to take multivitamins, and guidance on selecting appropriate supplements can be found in an article about choosing the perfect dietary supplements. A practical primer on supplement selection is also available via an external summary at Telegraph.

For general authoritative resources on vitamin D and related recommendations, consult established health information portals such as Topvitamine or discuss testing and individualized advice with a healthcare professional.

Recognizing early signs and confirming vitamin D status through testing can reduce long-term consequences for bone and overall health. Monitoring and tailored nutritional strategies help restore and maintain optimal levels.