What causes low levels of 25-hydroxyvitamin D, and what should I do?

In general, low levels of 25-hydroxyvitamin D may be caused by insufficient sunlight exposure, dietary deficiency, aging, chronic pancreatitis, vitamin D-dependent rickets, and other conditions, requiring management based on individual circumstances.

1. Insufficient Sunlight Exposure: Prolonged indoor work, limited outdoor activity, living in high-latitude areas, or residing in areas with severe air pollution can block ultraviolet rays, thereby reducing the skin's synthesis of vitamin D and leading to decreased levels of 25-hydroxyvitamin D. It is recommended to schedule regular outdoor activities daily or receive indirect sunlight exposure near a window.

2. Dietary Deficiency: Long-term vegetarian diets, picky eating habits, or rarely consuming foods rich in vitamin D can lead to inadequate vitamin D intake, resulting in reduced levels of 25-hydroxyvitamin D. It is recommended to adjust dietary patterns and increase the intake of vitamin D-rich foods such as milk and mushrooms.

3. Aging: With increasing age, the skin's ability to synthesize vitamin D declines, and the kidney's capacity to convert 25-hydroxyvitamin D into its active form also diminishes. It is recommended to supplement vitamin D under a physician's guidance, such as using ergocalciferol tablets or cholecalciferol injection.

4. Chronic Pancreatitis: Chronic pancreatitis damages the exocrine function of the pancreas, leading to reduced secretion of pancreatic lipase, which impairs digestion and absorption of fats, thereby affecting the absorption of vitamin D and causing decreased levels of 25-hydroxyvitamin D. It is recommended to take medications such as pancreatin enteric-coated capsules and pantoprazole sodium enteric-coated capsules under a physician's guidance.

5. Vitamin D-Dependent Rickets: This condition is mainly caused by gene mutations that disrupt vitamin D metabolic pathways, potentially impairing the liver's ability to perform the 25-hydroxylation of vitamin D. It is recommended to take medications such as calcitriol soft capsules and vitamin D drops under a physician's guidance.

Individuals with vitamin D deficiency should also undergo regular follow-up testing of serum levels to monitor changes and adjust treatment plans promptly.