Norinyl-1 Tablets

Norinyl-1 is a combined oral contraceptive tablet containing norethisterone 1 milligram and mestranol 50 micrograms per tablet, licensed in the United Kingdom for the prevention of pregnancy. Norinyl-1 belongs to the combined hormonal contraceptive group of medicines. It is available as a 21-tablet monophasic film-coated pack, taken on a 21-day active tablet, seven-day break schedule, and is manufactured by Pfizer Limited.

Most combined pills in the UK use ethinylestradiol as their oestrogen. Norinyl-1 does not exist. It uses mestranol — an oestrogen prodrug that your body converts to ethinylestradiol after you take it. This single difference gives Norinyl-1 a distinct pharmacological identity from every other combined pill on this site. Understanding what mestranol is, and what it means for how this pill behaves in your body, is the starting point for understanding Norinyl-1.

Think of mestranol as a dormant form of oestrogen. When you swallow a Norinyl-1 tablet, mestranol passes from your gut into your liver. Liver enzymes demethylate it, converting it into ethinylestradiol — the oestrogen that then enters the bloodstream and produces the contraceptive effect. The 50 microgram dose of mestranol therefore does not deliver 50 micrograms of active oestrogen directly. Conversion is not complete in every individual, but the resulting circulating ethinylestradiol levels are generally considered equivalent to a higher ethinylestradiol dose than the 20 to 35 microgram range used in modern combined pills.

This prodrug conversion is pharmacologically important. It places Norinyl-1 in a different clinical category from Norimin, which uses ethinylestradiol 35 mcg directly, even though both contain norethisterone 1 mg as the progestogen. The two pills are not clinically interchangeable without prescriber reviews.

Norethisterone is a first-generation synthetic progestogen derived from testosterone. Unlike third-generation progestogens such as desogestrel or gestodene, norethisterone retains mild androgenic receptor activity. At 1 mg this effect is modest, but it is worth knowing if you have previously experienced acne or oily skin on norethisterone-containing preparations.

After mestranol converts to ethinylestradiol in your liver, two hormones are at work simultaneously: the resulting oestrogen and norethisterone. They travel in your bloodstream to the hypothalamus and pituitary gland — the hormonal command centre in the brain that runs the menstrual cycle. Norinyl-1 sends a signal that convinces this system the body is already in a hormonal state incompatible with ovulation. Follicle-stimulating hormone and luteinising hormone are both suppressed. Without the luteinising hormone surge, the ovary does not release an egg.

That is the primary mechanism. But Norinyl-1 does not rely on it alone.

Norethisterone changes the physical character of cervical mucus throughout the active phase. The mucus becomes significantly thicker and less permeable. Sperm that reach the cervix face a hostile environment rather than a clear passage. This secondary barrier operates independently of whether ovulation suppression is complete on any given cycle.

A third mechanism operates at the level of the uterus itself. The hormonal environment created by Norinyl-1 maintains the endometrial lining in a state less suited to implantation. This layer of protection is rarely tested in practice because the first two mechanisms are so consistent — but it is there.

During the seven-day break, both mestranol converted oestrogen and norethisterone clear from your system. Hormone levels fall. The endometrium, which has been held in a hormonally suppressed state, responds by shedding. This produces withdrawal bleeds. It is not a period in the biological sense. It is the body responding to hormone withdrawal on a schedule set by the pill. Starting the next pack on day 29 restores suppression before the ovaries have time to resume their natural activity.

The most important rule with any combined pill is never to let the break go beyond seven days. A gap longer than seven days gives the ovaries time to begin follicle development. Once that process starts, a new pack may not re-establish suppression before an egg is released. Everything else about taking Norinyl-1 correctly flows from that central point.

When to start

Day 1 of your period gives you immediate protection — no additional contraception is needed. If you start between days 2 and 5, use a barrier method for your first seven days on the pill. If you switch from another combined pill, begin Norinyl-1 the day after your last active tablet from the previous pack. If your previous pill had inactive placebo tablets, start after the last of those. Coming from a progestogen-only pill, start on any day and use a barrier method for seven days.

The daily routine

One tablet at the same time every day for 21 consecutive days. Then stop for exactly seven days. Restart on day 29. Whether or not the withdrawal bleed has finished does not change the restart date. Day 29 means day 29.

If you vomit within two hours of taking a tablet, or have a significant bout of diarrhoea, the dose may not have been absorbed properly. Handle it as a missed tablet.

If you miss a tablet

Under 24 hours late — take it as soon as you notice. Carry on at the usual time. Protection is intact.

More than 24 hours late — take the missed tablet immediately. Take the next one at the usual time even if they land on the same day. Use a barrier method for the following seven days.

Two or more in a row — take only the most recently missed one. Discard the rest. Continue the pack. Use condoms for seven days. If those missed tablets were in week one and you had unprotected sex in the preceding seven days, emergency contraception may be needed. Do not wait — contact your prescriber or pharmacist on the same day.

Norinyl-1 comes in one strength. Every tablet in the 21-tablet pack contains norethisterone 1 milligram and mestranol 50 micrograms. The regimen is fixed: one tablet daily for 21 days, seven days off, and a new pack on day 29. No dose adjustment, no phase changes.

Where Norinyl-1 sits in the norethisterone family

Norethisterone is the progestogen in four UK-licensed contraceptive preparations. Understanding the differences helps clarify what makes Norinyl-1 distinct:

1. Norinyl-1: norethisterone 1 mg + mestranol 50 mcg (prodrug oestrogen — higher oestrogenic exposure)
2. Norimin: norethisterone 1 mg + ethinylestradiol 35 mcg (direct oestrogen — lower oestrogenic exposure)
3. Brevinor: norethisterone 500 mcg + ethinylestradiol 35 mcg (lower progestogen dose)
4. Noriday: norethisterone 350 mcg only (progestogen-only pill — no oestrogen at all)

Norinyl-1 is the only preparation in this family using mestranol. It is also the one with the highest overall oestrogenic exposure. This is the central clinical consideration when a prescriber compares it with Norimin for an individual patient.

Supply

Norinyl-1 does not have a generic equivalent in the current UK market. It is manufactured exclusively by Pfizer Limited. If your usual pharmacy cannot source it, they will need to order it specifically. Do not accept substitution — Norinyl-1 and Norimin are not interchangeable without clinical review.

Norinyl-1 shares the general side effect profile of combined oral contraceptives, but its higher oestrogenic exposure from the mestranol conversion introduces a nuance worth understanding.

Oestrogen-related effects

Nausea, breast tenderness, and fluid retention are oestrogen-driven side effects. Because Norinyl-1 delivers a higher circulating oestrogen level than lower-dose ethinylestradiol preparations, these effects may be more noticeable in some women than on a 20 or 30 microgram ethinylestradiol pill. If you have previously struggled with oestrogen-related side effects on combined pills, this is worth raising your prescriber before starting Norinyl-1.

Norethisterone-related effects

Norethisterone's mild androgenic activity means that a minority of women experience acne or oily skin. This is a first-generation progestogen characteristic and is less pronounced than in older, higher-dose preparations. Most women taking Norinyl-1 will not notice any skin change. Those with a history of androgen-sensitive skin on norethisterone preparations should mention this to their prescriber.

Mood and libido

Mood changes, including low mood or irritability, and changes in libido are commonly reported across combined pills. These are not unique to Norinyl-1 and are listed in the SmPC for most combined preparations. If you notice persistent mood changes after starting Norinyl-1, speak to your prescriber at your next review.

Less common effects

• Weight changes
• Contact lens intolerance from changes in corneal curvature
• Chloasma: skin darkening on the face, made worse by sun exposure
• Changes in vaginal discharge

Warning signs that need urgent attention

Stop taking Norinyl-1 immediately and call 999 or go to A&E if you experience:

• Sudden chest pain, difficulty breathing, or coughing up blood
• Swelling, heat, redness, or pain in one leg
• A sudden severe headache that is unlike your usual headaches, or any visual disturbance, speech difficulty, or one-sided weakness
• Acute severe abdominal pain
• Yellowing of the skin or the whites of your eyes

These may indicate a serious blood clot, stroke, or liver problem.

Blood clot risk and the mestranol dose

All combined pills carry a small increased venous thromboembolism risk above the baseline for women using no hormonal contraception. The higher oestrogenic effect of mestranol 50 mcg, relative to the ethinylestradiol doses used in modern combined pills, is a factor in the overall VTE risk assessment for Norinyl-1. Your prescriber evaluates your personal risk profile — BMI, smoking history, family history of clotting, planned immobility — before recommending this preparation. If you develop sudden leg pain, swelling, or breathing difficulty at any point while taking Norinyl-1, seek urgent medical attention.

Medicines that reduce effectiveness

Enzyme-inducing medicines accelerate the liver's processing of both mestranol and norethisterone, reducing circulating hormone levels. These include rifampicin, several antiepileptics including phenytoin, carbamazepine, phenobarbital, and topiramate, some HIV antiretrovirals, and St John's Wort. Tell your prescriber about every medicine and supplement you take, including anything available without prescription.

Norinyl-1 is not suitable if you:

• Have ever had a blood clot of any kind — DVT, pulmonary embolism, stroke, or heart attack
• Experience migraine with aura — this is an absolute contraindication to all oestrogen-containing combined pills, and the mestranol-derived oestrogen in Norinyl-1 carries the same risk as direct ethinylestradiol
• Have uncontrolled high blood pressure
• Have liver disease, liver tumours, or a history of jaundice caused by previous pill use
• Have a current or past diagnosis of breast cancer or any other oestrogen-sensitive malignancy
• Are pregnant or breastfeeding a baby under six weeks old
• Smoke and are 35 or older
• Have diabetes with established effects on your blood vessels, kidneys, or eyes

Norinyl-1 may be appropriate if you:

• Are a healthy adult woman with no contraindications to oestrogen-containing combined contraception
• Have been prescribed Norinyl-1 previously and are seeking a reviewed continuation prescription
• Do not have migraine with aura, are not a heavy smoker, and have no personal or family history suggesting elevated clotting risk

Discuss these points with your prescriber before starting:

• Smoking under 35 — cardiovascular risk applies at any age with oestrogen-containing contraception
• BMI above 30 — an independent VTE risk factor that influences the overall risk assessment
• Family history of clotting in a first-degree relative before age 50
• Any previous oestrogen-related side effects, as Norinyl-1's mestranol dose may produce higher oestrogen exposure than you have experienced before
• Planned surgery or immobility — temporary VTE risk elevation during recovery is relevant when you are already on a combined pill
• Depression or current mood disorder treatment

Getting a prescription for Norinyl-1 at Pharmacy Planet begins with a clinical questionnaire, not with a prescription. A registered prescriber reads your answers and makes an independent decision about whether this preparation is the right choice for you.

What makes Norinyl-1 consultations slightly more involved than consultations for most combined pills is the mestranol question. Mestranol's conversion to ethinylestradiol is well-understood pharmacologically, but it produces a different oestrogenic exposure profile from the direct ethinylestradiol preparations that most UK prescribers use day to day. A prescriber considering Norinyl-1 for you will want to understand your previous pill history, any oestrogen-related effects you have experienced, and whether the higher oestrogenic activity of this preparation is clinically appropriate or potentially problematic for you specifically.

The outcome may be a prescription for Norinyl-1, a recommendation for Norimin if a lower oestrogen exposure is preferred, a suggestion to try a different progestogen class entirely, a request for more information, or a referral for a face-to-face review. Completing the questionnaire opens clinical conversation. It does not guarantee any particular outcome. Repeat prescriptions are individually reviewed at each cycle of supply. There is no automatic renewal.

Norinyl-1 tablets do not need refrigeration. Store them below 25°C in a consistent location — a bedside table drawer or a cool kitchen cupboard works well. Avoid bathrooms, where heat and humidity from showers can degrade the foil blister over time. Keep the tablets in the original blister strip: the foil protects from moisture, and the day markings help you track your position in the pack.

Store all medicines out of the sight and reach of children. Check out the expiry date printed on the outer carton before beginning each new pack.

When you have unused or expired tablets, take them to any UK pharmacy. Pharmacies accept returned medicines for safe disposal at no charge, as part of the national Duty of Care framework. Flushing tablets or putting them in household rubbish harms the environment; returning them to a pharmacy is the correct disposal route.

This reference guide compares the contraceptive preparations available at Pharmacy Planet, grouped by delivery method and formulation type. Every preparation is a Prescription Only Medicine. A registered prescriber will review your individual health profile, contraceptive history, and risk factors before recommending any preparation. This table is a clinical reference, not a recommendation.

Combined Oral Contraceptive Tablets (Monophasic)

Monophasic combined pills contain the same dose of both hormones in every active tablet. The table below compares commonly prescribed monophasic combined oral contraceptives by progestogen type, oestrogen dose, VTE risk category, pack format, and key clinical characteristics.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Norinyl-1 is not a pill that a prescriber can assess by applying a standard combined pill checklist and moving on. The mestranol oestrogen type, the prodrug conversion dynamic, the higher oestrogenic exposure relative to modern low-dose pills, and the norethisterone progestogen's androgenic activity all require a prescriber who engages with the clinical detail rather than processing a routine contraceptive request.

At Pharmacy Planet, every consultation — including consultations for preparations as specific as Norinyl-1 — is reviewed by a registered prescriber who reads your individual history and makes a considered clinical decision. If Norinyl-1 is not the most appropriate option for your circumstances, you will be told that and offered a clearer path forward. That is what responsible prescribing looks like.

• Pfizer Limited. Norinyl-1 tablets — Summary of Product Characteristics. Available at: www.medicines.org.uk/emc. Accessed May 2026.
• Faculty of Sexual and Reproductive Healthcare (FSRH). Combined Hormonal Contraception — Clinical Guidance. Available at: www.fsrh.org. Accessed May 2026.
• NHS. Combined pill — your contraception guide. Available at: www.nhs.uk/conditions/contraception/combined-contraceptive-pill. Accessed May 2026.
• British National Formulary (BNF). Norethisterone with mestranol. Available at: bnf.nice.org.uk. Accessed May 2026.
• MHRA. Combined hormonal contraceptives and venous thromboembolism — updated guidance. Available at: www.gov.uk. Accessed May 2026.