Oral hormonal contraception: a practical guide

Despite availability of newer, more effective and longer-acting methods, such as hormonal intrauterine devices (IUDs), implants and injectables, oral hormonal contraception remains one of the most widely used methods of contraception in the UK^​1,2​. The term encompasses two main categories: combined oral contraception (COC), which contains both an oestrogen and a progestogen, and progestogen-only pills (POP), which contain a progestogen alone. These preparations are highly effective when used correctly and offer additional non-contraceptive benefits for some users, including menstrual management^​3,4​. However, their use requires careful assessment, counselling, strict adherence and follow-up to ensure safety and effectiveness^​3,4​.

UK oral contraception use appears to be shifting away from traditional GP/specialist sexual and reproductive healthcare prescribing towards pharmacy access; however, total use of oral contraception is hard to measure because these datasets are not currently linked. In recent years, the role of pharmacists in contraception prescribing has expanded significantly. In England, the introduction of the NHS pharmacy contraception service in April 2023 has enabled community pharmacists to supply oral contraception for ongoing use, aligning with the ‘NHS long-term plan’, which outlined aims to improve access and reduce health inequalities^​5,6​.

Similar developments are under way across the rest of Great Britain, reflecting a broader shift towards pharmacy-led provision of sexual and reproductive healthcare. In Scotland, some pharmacies can provide an initial three-month supply of the POP as ‘bridging contraception’, which is a supply to ensure protection against pregnancy before obtaining long-term contraception^​7​. In Wales, services mirror that of England, while some pharmacies provide both ‘bridging contraception’ as well as routine long-term oral contraception^​8​. 

Pharmacists are well placed to support the safe use of oral contraception owing to their accessibility, medicines expertise and frequent contact with patients. Their role includes supporting informed contraceptive choice, identifying contraindications, managing drug interactions and monitoring ongoing use. This article provides a practical, evidence-based overview of oral hormonal contraception, with a focus on eligibility assessment, initiation and monitoring.

What are the different types of oral contraception?

Combined oral contraception

COC contains both oestrogen (usually ethinylestradiol) and a progestogen. The primary mechanism of action of COC is suppression of ovulation via action on the hypothalamic-pituitary-ovarian axis by suppressing luteinising hormone (LH) and follicle-stimulating hormone (FSH), with additional effects on cervical mucus and the endometrium^​3​. When taken consistently and correctly, COCs are highly effective, with a perfect-use failure rate of approximately 0.3% but a typical-use failure rate of around 9.0%^​9​.

COC is available as either monophasic (constant dose) or phasic (variable-dose) preparations^​3​. Monophasic COC contain the same dose of ethinylestradiol (typically 20–35 μg) and the same dose of progestogen in each active pill^​3​. They are often still used in standard 21-day regimens followed by a seven-day pill-free interval (or placebo tablets for everyday formulations designed to help adherence). However, they can also be used in extended (shortened pill-free interval regimens) or continuous regimens (active pills are taken consecutively over several cycles)^​3,10​. While off license, these tailored regimens are supported by the College of Sexual and Reproductive Healthcare (CoSRH) with evidence that extended use may improve adherence, reduce contraceptive failure, and decrease hormone-withdrawal bleeding and menstrual-related symptoms (see Figure 1)^​3,10​.

Figure 1: Combined oral contraception dosing regimens

Phasic COC contain different doses of oestrogen and/or progestogen across the cycle^​3​. These preparations were designed to mimic endogenous hormonal fluctuations; however, they have not been shown to offer improved contraceptive efficacy nor tolerability compared with monophasic pills^​3​. Owing to variation in hormone dose across the cycle, phasic preparations offer less flexibility; tailored regimens are not recommended, missed-pill advice is more complex, and they are less commonly used^​3​.

COCs may confer non-contraceptive benefits, including improved cycle control, helping to reduce heavy menstrual bleeding and dysmenorrhoea, and improving acne symptoms. However, they are associated with specific risks including an increased risk of venous thromboembolism (VTE), stroke and myocardial infarction, particularly in individuals with additional risk factors such as smoking, obesity, immobility or older age^​11​. As a result, careful assessment using the UK Medical Eligibility Criteria (UKMEC) is essential before initiation^​11​. The UKMEC categorises the safety of contraceptive methods according to an individual’s medical conditions and risk factors. Categories range from UKMEC 1 (where there is no restriction to use) to UKMEC 4 (where the method presents an unacceptable health risk and should not be used). The clinical focus is on identifying UKMEC 4 and UKMEC 3 (where the risks outweigh the benefits and specialist clinical judgement may be required). While UKMEC 2 indicates that benefits generally outweigh the risks, careful consideration should be given where multiple category 2s exist for the same individual owing to concurrent characteristics or conditions^​11​.

Hormonal side effects are commonly reported by patients taking COCs, but may be short-lived (See Table 1)^{​3,4,9,12​}.

Progestogen-only pills

By contrast, POPs contain synthetic progestogen only. The contraceptive effect of desogestrel and drospirenone POPs relies primarily on inhibition of ovulation. Levonorgestrel and norethisterone (often referred to as ‘traditional’ POPs) do not reliably suppress ovulation. They act on cervical mucus, endometrium and tubal motility^​4​. All POPs are taken daily without a pill-free interval; however, in the drospirenone progestogen-only pills (DRSP POP) (Slynd), there are 24 active, followed by four placebo pills. The aim of the four hormone-free days is to try to establish a more predictable bleeding pattern, while maintaining contraceptive effectiveness^​4​[3]. When taken correctly, POPs have a similar failure rate as COC^​9​. POPs are generally safe and are suitable for individuals who cannot use oestrogen-containing contraception, including those with a history of VTE, migraine with aura or hypertension. Common side effects include altered bleeding patterns, headaches, breast tenderness and acne, although many are temporary (see Table 1)^{​3,4,9,12​}.

Table 1: Oral contraceptive pills: characteristics and clinical considerations

Initiation of oral hormonal contraception

When initiating oral hormonal contraception, pharmacists must adopt a patient-centred approach, accounting for reproductive intentions, experience and preferences, medical history and relevant lifestyle factors. Shared decision-making, supported by clear, unbiased, evidence-based information, improves satisfaction and continuation rates^​13​. 

Medical history

A comprehensive medical history must be obtained, including current and past medical conditions (e.g. migraine history and conditions with known risk for VTE), relevant personal characteristics (e.g. age, BMI, smoking status) and relevant family history (e.g. VTE, breast cancer). Medical eligibility should then be assessed in line with the UKMEC^​11​. For COC, blood pressure measurement is mandatory prior to initiation, and BMI should be recorded, as obesity is a known VTE risk factor. POPs require fewer baseline assessments. However, documentation of baseline weight and blood pressure is considered good practice^​4​. Refer to UKMEC guidance for specific information on blood pressure measurements^​11​.

Pregnancy and breastfeeding

Pharmacists involved in initiation should ensure that postpartum status and breastfeeding are routinely assessed and documented, with eligibility assessed via the UKMEC^​11​. Contraception is generally required from day 21 after childbirth if pregnancy is not desired. VTE risk is significantly elevated during pregnancy and the postpartum period; this risk is most pronounced in the first three weeks after delivery, declining to near baseline levels by 42 days postpartum^​14​.

The evidence regarding the effects of COC on milk supply is limited and conflicting, therefore women who are breastfeeding are advised to wait until six weeks after childbirth before initiating a COC^​11​. 

POPs can be started at any time after childbirth, including immediately after delivery and the evidence indicates no adverse effects on lactation, infant growth or development^​4,14​.

Drug history

Healthcare professionals providing hormonal contraception should take a detailed drug history including current and previous drug use, which covers prescription, online, over-the-counter (OTC), herbal, recreational drugs and dietary supplements^​11​. Potential drug interactions must be assessed, particularly with enzyme-inducing medicines (such as certain antiepileptics, antiretrovirals and antibiotics, as well as herbal OTC medicines available, e.g. St John’s wort) or glucagon-like peptide-1 (GLP-1) agonists, which may reduce contraceptive efficacy^​15,16​. Effective contraception is recommended during use of GLP-1 agonists, owing to a lack of safety data available for use of GLP-1 agonists in pregnancy. For individuals using tirzepatide with oral contraception, a switch to a non-oral method or additional barrier contraception is advised for four weeks after initiation and after each dose increase^​16​. 

Patient preference 

A tailored discussion of side effects is important. Some individuals may prefer regular withdrawal bleeding, while others may favour reduced bleeding or amenorrhoea. Previous experiences with hormonal contraception — including tolerability and side effects — should inform shared decision-making. It is helpful to explain that side effects with oral hormonal contraception are often short lived and may usually settle within the first few months. Reproductive intentions should be reviewed, including short- and long-term pregnancy plans, desire to avoid pregnancy and expectations regarding return to fertility after stopping contraception. Patients should be counselled regarding the relative efficacy of methods and advised that fertility typically returns rapidly following discontinuation of oral hormonal contraception^​3,4​.

The individual’s ability to maintain daily dosing, work patterns, travel, shift work and the need for privacy or discretion is relevant. Where daily adherence is likely to be challenging, alternative methods, including long-acting reversible contraception (LARC), may be preferred. Travel considerations, including time zone changes and access to supplies abroad, should be discussed. Clear written information can reinforce verbal counselling and support adherence. The consultation should address sexual health and safeguarding considerations. As oral contraception does not protect against sexually transmitted infections (STIs), patients should be advised about condom use and signposted to STI testing. Pharmacists should remain alert to safeguarding concerns, including coercion, difficulties accessing contraception or challenges with follow-up, and act in accordance with local safeguarding policies.

Timing of initiation

COC can be initiated up to and including day five of the menstrual cycle without the need for additional contraceptive precautions, provided pregnancy can be excluded. See Box 1 of the CoSRH guideline on combined hormonal contraception for criteria for reasonably excluding pregnancy^​3​. If COC is initiated after day five of the menstrual cycle, a “quick start” approach may be used. In this scenario, additional barrier contraception is required for the first seven days of pill use, and a follow-up pregnancy test is recommended three weeks after the last unprotected sex if there is a risk of conception prior to initiation^​3​.

Traditional and desogestrel POPs provide immediate contraceptive protection when initiated between days one and five of the menstrual cycle. If initiated at any other time in the cycle, additional barrier contraception is required for 48 hours^​4​. DRSP POP must be started on day one of the menstrual cycle for immediate contraceptive protection^​4,7​. If started at any other time additional barrier contraception is required for seven days^​17​ (see Figure 2).

Figure 2: Timing of initiation of oral hormonal contraception

How to take

COCs are taken daily and consistent timing is important to maintain contraceptive efficacy. The standard regimen for monophasic COCs is 21 consecutive active pills followed by a seven-day hormone-free interval (HFI) before starting the next pack. The seven-day break can be either pill-free days or placebo tablets, depending on the product^​3​. However, tailored (extended or continuous) regimens are safe, effective and increasingly preferred^​10​. It should be advised to women that a withdrawal bleed does not represent physiological menstruation and has no health benefits^​3​.

POPs are taken daily without a pill-free interval, and consistent timing is again important to maintain contraceptive efficacy^​4,7​.

Missed-pill rules

A COC pill is considered missed if it is more than 24 hours late. Missing a single COC pill is insufficient to reverse ovarian suppression; however, missing two or more, or extending the HFI, by missing pills at the end of a packet or forgetting to restart the new packet on time, increases the risk of ovulation^​3​.

For further guidance on missed-pill rules with COC, follow CoSRH guidance^​18​.

Traditional POPs are considered missed if taken more than three hours late, a desogestrel POP if it is taken more than 12 hours late, and a DRSP POP if more than 24 hours late. 

Recommended actions after incorrect POP use are set out in Table 1, Appendix 2 and Appendix 3 of CoSRH guidance^​4​. Recommendations for DRSP POP differ from those for other POPs.

Missed pill guidance varies between different formulations but when doing an initial ‘pill teach’ with patients, the following simplified common rules can be used:

• Take the last missed pill as soon as remembered;
• Take the next one when it was due (even if that means taking two in one day);
• Continue to take future pills daily at the usual time;
• Use condoms for seven days (CHC or DRSP POP) or 48 hours (traditional and desogestrel containing POP);
• Omit the HFI “break” or placebo pills (CHC or DRSP POP) if missed pills in the seven days before any scheduled break;
• If you’ve had sex and are unsure what to do, seek advice regarding emergency contraception and bring your pill packets with you if possible^​18​. 

Women using oral contraception should also follow the instructions for missed pills if vomiting occurs within two to three hours of taking or severe diarrhoea occurs for over 24 hours and consider non-oral contraception if diarrhoea or vomiting persist^​3,4​.

Additional considerations

Monitoring and review

After initiation, patients should be reviewed at about three months. Thereafter, annual review is recommended for most users, although more frequent review may be required if clinical circumstances change^​3​.

A routine review should assess tolerability, adherence and satisfaction. Changes in medical history, new medications, side effects and any concerns should be discussed and alternative methods considered as appropriate. Blood pressure measurement is required for each COC review. Pharmacists should also reinforce key counselling messages and ensure that the chosen method continues to align with the patient’s preferences and lifestyle^​3,4​. 

Stopping oral contraception may occur for a variety of reasons, including side effects, running out of supply, changing reproductive intentions or medical contraindications. If considering stopping, pharmacists should discuss alternative contraceptive options to prevent unintended pregnancy, including transition to another method. Individuals who have stopped hormonal contraception suddenly may need emergency contraception. Individuals planning pregnancy should be advised that fertility returns rapidly after stopping oral contraception and offered preconception counselling, including folic acid supplementation and optimisation of management of medical conditions, where appropriate^​3,4​.