How long does it take for tetracycline to work?

Tetracycline, a drug that treats bacterial infections, may take several weeks to several months to work, according to Acne.com. It is commonly prescribed along with topical medications to treat acne although it is used for other infections as well, reports MedlinePlus.

Tetracycline is usually prescribed to be taken from two to four times a day, reports MedlinePlus. Patients are advised to take this drug regularly and at the correct dosage. Pneumonia and other respiratory tract infections as well as some ulcers are also commonly treated with tetracycline. If the drug is discontinued before a treatment cycle is completed, then symptoms are likely to return, warns Acne.com.