Iron Sucrose in Patients With Iron Deficiency and POTS

Inclusion Criteria: * Patients (age 12 to years and older) with chronic (\>3 months) symptoms of orthostatic intolerance, including but not limited to lightheadedness, syncope, headache, fatigue, weakness, sweating, nausea and heart palpitations. * Symptomatic orthostatic heart rate increment ≥30 bpm if \>19 years old or ≥40 bpm if \<19 years old during a 10 minute 70 degree head up tilt study * Presence of non-anemic iron deficiency, defined as serum ferritin levels \<20 ug/L with hemoglobin no less than 1 gm/dL below the normal reference range as defined for age and gender * Consent obtained from responsible guardian AND from subjects, 12-17 years of age * Consent obtained for subjects 18 years of age and older Exclusion Criteria: * Orthostatic hypotension (decrease of systolic BP\>30 mmHg and/or diastolic BP\>15mmHg within 3 minutes of 70 degree head up tilt study) * Pregnant or lactating females * The presence of failure of other organ systems or systemic illness that can affect autonomic function * Concomitant therapy with anticholinergic, alpha-adrenergic antagonists, beta-adrenergic antagonists or other medications which could interfere with autonomic testing. Patients may participate if the potentially interfering medication is held for five half-lives prior to the study * Laboratory evidence of anemia or iron overload * Personal history of hematochromatosis or first degree relative with hematochromatosis * Known sensitivity to Venofer® (iron sucrose injection, USP) or other intravenous iron preparation