OBJECTIVES: More than 10% of adolescents suffer from severe fatigue and/or orthostatic intolerance. Adult studies show correlations between iron insufficiency and fatigue as well as between hypovitaminosis D and non-specific pain. We sought to determine whether there were correlations between nutritional factors (iron status, and serum vitamin D levels) and chronic ill health. METHODS: We reviewed records of 188 adolescents with symptoms of fatigue and/or orthostatic intolerance and who underwent autonomic reflex screening. RESULTS: Of the 188 patients, 130 patients (69%) had excessive postural tachycardia (PT) with a heart rate (HR) change of ≥30 bpm. 62 patients (47%, n = 131) had iron insufficiency with low iron stores, and 29 patients (22%, n = 131) were iron deficient. HR change did not correlate to ferritin level (P = 0.15). 21 patients (22%, n = 95) had hypovitaminosis D (25-hydroxyvitamin D ≤20 ng/mL). There was a significant association with hypovitaminosis D and orthostatic intolerance (P = 0.024). CONCLUSION: In patients presenting with chronic fatigue and/or orthostatic intolerance, low ferritin levels and hypovitaminosis D are common, especially in patients with PT.