Why choose 20mcg contraceptive pill instead of 30mcg pill?

Comprehensive information about low dose contraceptive pills.

The development of low dose pills

When the combined pill was first developed in the 1960s, it contained a comparatively high dose of estrogen. However as clinical experience with the pill accumulated, it was realised the same contraceptive effect could be obtained using far lower doses of hormones.

Over the past 50 years, in order to improve the safety of the pill, and to reduce the side effects, the types of hormone in the pill have been altered, and the dose of hormones lowered dramatically. There are now a wide variety of different pill brands.

When you consider 20mcg pills, women can now take less hormone in a week, than they used to take in a day.

The standard dose of ethinylestradiol in the pill is 30-35mcg. Any pill with a lower dose of estrogen is called a low dose pill.

Which is the best pill?

Women often ask 'which is the best pill?'. The simple answer is that all women are different, and thankfully there are a range of pill options which usually means there will be a pill brand out there to suit you. There isn't really a 'best pill' – it's just important to find the best one for you.

What do we know about 20mcg pills?

  • 20mcg combined pills contain 30% less estrogen than other combined pills. However these are still a recommended and reliable form of contraception.

    There has been some speculation that Loestrin 20 may have a slightly higher failure rate, but studies are small and overall inconclusive.

    It has been noted that over the past 50 years, as the dose of hormones in the pill has been reduced, pill failures in clinical trials have gone up. 20mcg pills do give safe reliable contraception, but for some women, the added safety of a standard 30mcg pill, may be preferable.

  • The only second generation 20mcg pill is Loestrin 20. All the others are third generation pills. More information about the difference between second and third generation pills.

  • It has been difficult to prove that the thrombosis (blood clot) risk is actually lower on 20mcg pills than 30mcg pills in clinical studies, but these pills do have less effect on clotting factors.

  • Lowering the estrogen dose is not suitable for everyone, and may result in side effects such as bleeding. Estrogen is beneficial. It tends to improve acne, and also helps stabilise bleeding patterns.

  • A 20mcg pill may be helpful for example if a standard pill causes nausea or vomiting. These are usually an estrogenic side effect.

  • Bleeding patterns are slightly less favourable with 20mcg pills (study), and more favourable on 30mcg pills (study).

  • 20mcg pills may only be prescribed subject to the same medical recommendations as 30mcg pills. Even though they contain a lower dose of estrogen, they still generally regarded as having the same risks and benefits as other pills.

  • Pill failures seem to be slightly more common if you take the pill and are overweight (BMI greater than 30), although there is not a lot of medical evidence to support this. Somehow it seems, BMI may be linked to contraceptive efficacy. You should discuss the choice of your pill with your doctor.

  • You can run packs of 20mcg pills together to avoid periods – running 3 months at a time is called tricycling. This has added advantages for contraception.

    If however you do this and bleed midcycle, one option is to use a similar 30mcg alternative to do this temporarily, and go back on your 20mcg pill in due course – say after your holiday.

    For example if you are on Loestrin 20, take Loestrin 30 for the period of your holiday, then have the 7-day break and go back on Loestrin 20.

  • Fit, healthy, non-smoking women can use the combined pill until they are 50. It may be an option to reduce to a 20mcg pill in older women, whose natural fertility is declining with age, and for whom a lower dose of estrogen may reduce cardiovascular/stroke risk. This should be discussed with your doctor.

Illustration of patient leaflet from medicine packet

20mcg pill brands

Below is a list of currently available (Dec 2018) 20mcg pills, with links to the Patient Information Leaflet for each (the leaflet included in the medicine packaging which includes directions on how to take). They are all 21-day regimes, followed by a 7-day break.

UK brands of 20mcg contraceptive pills - packet photo
UK brands of low-dose 20mcg contraceptive pills

Where can I get a 20mcg pill?

All contraceptive pills are prescription only medicine (POM).

  • Make an appointment with your GP/practice nurse.
  • Visit NHS - Find a Sexual Health Clinic – type in your postcode to find the nearest specialist clinic to you.
  • Dr Fox are only able to prescribe contraceptive pills you are already taking, so if you want to swap to a new pill brand, you must see your doctor/nurse or visit a clinic.
Buy Contraceptive Pill

Authored 14 November 2018
by Dr Tony Steele

Last updated 29 October 2021

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