How to take Ceftriaxone. Use exactly as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label. Ceftriaxone is injected into a muscle, or into a vein through an IV. You may be shown how to use an IV at home. Do not self-inject this medicine if you do not fully understand how to give the injection and properly dispose of used needles, IV tubing, and other items used to inject the medicine. Ceftriaxone must be given slowly, and the IV infusion can take at least 30 minutes to complete.