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Oral Contraceptives

Oral Contraceptives

Oral contraceptive, when taken consistently and correctly, is a highly reliable (over 99% effective) and non-permanent means for contraception.

How do oral contraceptive pills achieve contraception?
  1. preventing ovum development and ovulation;
  2. suppressing development of uterine lining and discouraging implantation of eggs; and
  3. thickening the cervical mucus and making it difficult for sperms to reach the eggs in the uterus.


Composition and Classification of Oral Contraceptive Pills

Oral contraceptive pills can be divided into the following two categories according to their composition:

  1. Combined Oral Contraceptive (COC) pills:
    COC pills contain two hormones, oestrogen and progestogen. Their composition is designed to resemble the endocrine cycle of women and therefore pills are taken on a 28-day cycle. They are generally available in 21-pill and 28-pill packs:
    • 21-pill packs contain 21 hormonal pills. You have to stop for seven days after consumption of one pack before starting the second pack.
    • 28-pill packs contain 21 hormonal pills followed by 7 non-hormonal pills; or 24 hormonal pills followed by 4 non-hormonal pills.
  2. Progestogen-only Contraceptive pills (POPs)
    POPs only contain progestogen (a hormone). You should take one pill per day without any break.


Use and Choice of Oral Contraceptive Pills

Different preparations contain different dosage of hormones to suit different physical conditions among women. The use of oral contraceptive pills should be started under the advice of a doctor and continued under medical supervision. While you are taking oral contraceptive pills, you should see a doctor at least once a year for advice on suitability of continued use.


Common Side Effects of Oral Contraceptive Pills*

Common side effects of oral contraceptive pills include headache, nausea, vomiting, breast tenderness, fluid retention, changes in weight and sex desire, and depressed mood. Taking oral contraceptive pills may also increase the risk of thrombosis and slightly increase the risk of breast cancer. Not all women are suitable to take oral contraceptive pills and therefore medical advice is required for the use of oral contraceptive pills.

If you are worried about a side effect or you notice anything unusual, please seek advice from a doctor or a pharmacist.


General Contraindications for Taking Oral Contraceptive Pills*

Women should not take oral contraceptive pills if they are:

  • suffering from arterial/venous blood clots or having a medical history or symptoms of thrombosis such as heart disease, stroke and blood clots in vessels supplying the legs or the lungs;
  • suffering from jaundice, liver disease, hepatic disorder or liver tumour;
  • suspected or confirmed patients of breast or reproductive organ cancer;
  • suffering from vaginal bleeding of unknown reasons;
  • suffering from diabetes with complications;
  • smokers over 35 years of age (should not take combined oral contraceptive (COC) pills); and
  • suspected or known pregnancy.

General Advice on Taking Oral Contraceptive Pills*

  • You should seek advice from a doctor before taking oral contraceptive pills.
  • Do not exceed the length of treatment/dose as recommended or prescribed by a doctor
  • You should seek advice from a doctor if any of the following occurs while taking oral contraceptive pills:
    1. You have missed a dose or taken a wrong dose;
    2. You are going to receive a surgery or require prolonged bed rest in the coming one or two months’ time;
    3. You have to take other drugs as well and in particular, antispasmodics, antibiotics or tranquillizers (as certain drugs may interfere with the effect of oral contraceptive pills);
    4. You have been vomiting or have diarrhoea that persists for more than 24 hours;
    5. Your menstruation does not start one week after you have taken non-hormonal pills or stopped medication;
    6. You are diagnosed with a new disease, e.g. heart disease, stroke, cancer, diabetes mellitus, thromboembolic disease, hypercholesterolemia or other newly diagnosed medical and surgical diseases.

Storage of Oral Contraceptive Pills

Oral contraceptive pills should be stored in a dry and cool place. They do not need to be refrigerated. Also, they should be stored properly to avoid accidents of mistaken consumption by children.

* Information contained herein may not cover all possible side effects, precautions, warnings, contraindications, drug interactions, allergic reactions, or adverse effects.



Drug Office
Department of Health
Oct 2023
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