I have uti. given amoxicillin. checked the capsules and there was only 18 instead of 21 tabs. would it make a difference if i miss a dose?

Possibly: If your clean catch urine culture,colony count and sensitivity confirms that amoxicillin would be effective treatment for your uti, a full week's or 10 day course is recommended. Ask your pharmacist to give you a total of at least 21 capsules for 3 times a day dosage.

Amoxil: By the time you take the last day' s dose you should hopefully be cured