Recently diagnosed with low iron serum level of 27. could this cause tachycardia? recently my resting heart rate is 98-105 bpm and im currently taking 25 mg of metoprolol er daily?

Low iron per se doesn't cause tachycardia but iron deficiency anemia could but usually with exertion. Resting sinus tachycardia can be seen in overactive thyroid, fever, with certain medications, excess alcohol or caffeine use, anxiety and inappropriate sinus tachycardia syndrome. Elevated total iron binding capacity is seen in true iron deficiency. Low iron alone is seen in chronic inflammation.