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Do not take them if the expiry date is passed (crossed more than a month's time) as they might lose their efficacy and will not prove useful. You can consider giving them back in exchange for new ones to your pharmacy, or visit your gynecologist for fresh prescription after repeat evaluation (to rule out any contraindications for the hormonal birth control use). Once you get started on the birth control pills, be regular with taking the pills at scheduled time daily. Use back-up protection if having intercourse during first few weeks of starting with birth control as most hormonal birth control methods start giving you effective protection after about 3-4 weeks of regular use. Consider being in regular follow-up and monitoring of your treating gynecologist and report any abnormal/new symptoms immediately. Take adequate rest. Drink plenty of water. Maintain healthy diet and lifestyle.
Take care.