I test my own blood and adjust my dosage of warfarin. Usually I'm right in range 2.5 to 3.5 (2 art heart valves). About 6 to 8 weeks ago, I took augmentin for 10 days, 2 weeks ago, I took another antibiotic for 5 days. Since then, my PT/INR has been too low, 2.0. My diet and meds have stayed the same. I've been increasing my dose, yet it's still too low. Is it normal for this change? Please see my profile! Can it indicate my lupus activity?