Clindamycin dosage. Clindamycin comes in 150 milligram (mg) and 300 mg capsules. You should receive no more than 4,800 mg of clindamycin in a day, and that dose is normally only for people receiving clindamycin via injection into the thigh. It’s very important that you continue taking the medication as prescribed until you have finished it all, even if your symptoms improve and you start to feel better.