If you experience frequent genital herpes outbreaks, there's an approach that goes beyond treating each flare-up as it arrives. Suppressive therapy involves taking a low daily dose of an antiviral such as aciclovir or valaciclovir every day to prevent outbreaks from occurring, reduce viral shedding, and lower the risk of passing herpes to a partner. This guide covers who it's most suitable for, what the clinical evidence shows, and what to expect from long-term daily antiviral medication for herpes.
What Is Suppressive Therapy and How Does It Work?
Genital herpes is caused by herpes simplex virus (HSV), a virus that stays dormant in the body after the first infection and can reactivate to cause recurring outbreaks. For people who experience frequent recurrences, taking antiviral medication every day rather than only during an outbreak is an option worth considering. This approach is called suppressive therapy, and it's one of the two main strategies for managing genital herpes long-term.
The two antivirals used for suppressive therapy in the UK are aciclovir and valaciclovir. Both work by interfering with the virus's ability to replicate, keeping the viral load low enough to prevent most outbreaks from occurring. Valaciclovir is a prodrug that the body converts into aciclovir, and its advantage is that it's absorbed more efficiently, meaning a lower dose taken less frequently achieves a comparable effect.
Who Should Consider Genital Herpes Suppression Treatment?
Suppressive therapy isn't necessary for everyone with genital herpes. It's most relevant if:
- You're having six or more outbreaks per year
- Your outbreaks are severe, prolonged, or causing significant distress
- You're in a relationship with a partner who doesn't have herpes and want to reduce transmission risk
- Recurrences are affecting your mental health, relationships, or quality of life
BASHH guidelines note that the threshold for starting suppressive therapy is a subjective decision made in partnership with your clinician, and factors like relationship status and individual impact on daily life should all inform it.1
What Doses Are Used?
The standard suppressive doses in the UK for people who experience six or more episodes a year are:
- Aciclovir - 400 mg twice daily (or 200mg four times a day)
- Valaciclovir - 500 mg once daily (for people with up to ten recurrences per year)
Where standard doses don't provide adequate control, your clinician may consider stepping up to aciclovir 200 mg four times daily or switching to valaciclovir, as individual absorption of aciclovir varies.3 These are prescription-only medicines, so you'll need a consultation to be prescribed them. Pharmica offers online consultations for both aciclovir and valaciclovir, with discreet delivery once prescribed.
How Effective Is Suppressive Therapy?
The evidence base for suppressive therapy is well established. Clinical studies have shown that daily antiviral medication reduces herpes recurrence frequency by 70 to 80% in people who previously experienced frequent outbreaks.2
Suppressive therapy also reduces viral shedding, including the asymptomatic shedding that occurs between outbreaks when no visible symptoms are present but the virus can still be passed on. Aciclovir and valaciclovir have been shown to suppress both symptomatic and asymptomatic shedding by 80 to 90%.3
On transmission specifically, a landmark clinical trial published in the New England Journal of Medicine in 2004, involving 1,484 couples where one partner had HSV-2, found that once-daily valaciclovir reduced the risk of acquiring herpes by 48% and the risk of developing symptomatic genital herpes by 75%.2 Suppressive therapy reduces but doesn't eliminate transmission risk, so using condoms alongside daily medication offers the most comprehensive protection.
How Long Do You Take It For?
Suppressive therapy is typically recommended for a minimum of six months initially. After twelve months of continuous treatment, BASHH guidance recommends a review to assess whether your circumstances have changed and whether you'd like to consider stopping.1 Some people find that outbreak frequency has naturally decreased over time and they no longer need daily medication. Others choose to continue long-term.
There can be a rebound outbreak within a few days of stopping, so it's sensible to discuss the timing with your prescribing clinician and have episodic treatment to hand.
Long-term suppressive therapy with aciclovir and valaciclovir has a good safety profile. Studies of up to 24 months show minimal side effects, with headache, nausea, and diarrhoea reported at rates comparable to placebo. No routine blood monitoring is needed in healthy adults without kidney problems.
Suppressive Therapy vs Episodic Treatment
Episodic treatment means taking antivirals only when an outbreak occurs, typically for two to five days, to shorten its duration and severity. It's a reasonable choice if your outbreaks are infrequent and mild. Suppressive therapy is the better option if outbreaks are frequent, unpredictable, or significantly affecting your daily life.
One practical consideration is that episodic treatment works best when started within 24 hours of the first symptoms, such as tingling or itching. If your outbreaks come on quickly, or you'd rather not manage them reactively, daily herpes medication removes that pressure.
Practical Tips for Taking Suppressive Therapy
- Take it at the same time each day - consistent timing helps maintain steady levels of the drug in your body.
- Don't double up if you miss a dose - take it as soon as you remember unless it's close to your next scheduled dose.
- Combine with safer sex practices - condoms significantly reduce transmission risk further and work well alongside daily medication.
- Declare other medications - aciclovir can interact with some medicines, including mycophenolate mofetil used in transplant patients. Always tell your GP or pharmacist what else you're taking.
- If outbreaks continue - don't assume the medication isn't working without speaking to your clinician first. Your dose may need adjusting.
When to Seek Further Advice
Contact your GP or a sexual health clinic if you:
- Are still having outbreaks despite taking suppressive therapy
- Develop new or unusual symptoms that could indicate a complication
- Are pregnant or planning to become pregnant, as specific guidance applies
- Have a weakened immune system, as standard suppressive doses may not be sufficient
- Experience side effects that are persistent or concerning
- Want to reassess whether to continue or stop treatment after twelve months
A full list of known side effects and interactions is available in the patient information leaflet supplied with your medication.
Frequently Asked Questions
Can you still transmit herpes while on suppressive therapy?
Yes, though the risk is significantly reduced. Suppressive therapy doesn't eliminate asymptomatic viral shedding entirely, it suppresses it. The landmark NEJM 2004 trial found that once-daily valaciclovir reduced the risk of transmission by around 48% in couples where one partner had HSV-2.2 For the most comprehensive protection, combining daily antiviral medication with condoms is recommended, as the two approaches work together.
Do you have to take herpes medication every day for it to work?
Yes, that's the core principle of suppressive therapy. Unlike episodic treatment, which is taken reactively during an outbreak, suppressive therapy only works if taken consistently every day. Missing doses can allow viral replication to increase and may reduce the protection it provides. Taking your tablet at the same time each day makes it easier to stay consistent.
How do you know if suppressive therapy is working?
The clearest sign is a significant reduction in the frequency of outbreaks. Most people on suppressive therapy experience far fewer recurrences than before, and some have none at all during treatment. If you're still having regular outbreaks after several weeks on the standard dose, speak to your clinician, as your dose may need reviewing or increasing.
Can suppressive therapy reduce herpes recurrence triggers?
Suppressive therapy works by keeping viral replication consistently low, which means common triggers such as stress, illness, or UV exposure are less likely to tip the balance into a full outbreak. It doesn't eliminate the underlying triggers themselves, but it raises the threshold at which they're able to cause a recurrence. Managing lifestyle factors alongside medication remains worthwhile.
Is there a daily medication for herpes available on the NHS?
Yes. Both aciclovir and valaciclovir are available on NHS prescription for suppressive therapy. Your GP or a sexual health clinic can assess whether you meet the criteria and prescribe accordingly. They're also available through regulated online pharmacies such as Pharmica following an online consultation, which some people find more convenient.
What happens when you stop suppressive therapy?
Outbreaks may return as the virus is no longer being suppressed. There can be a rebound outbreak within a few days of stopping, so BASHH guidance recommends planning this with your clinician and having episodic treatment available just in case.1 After stopping, it's worth monitoring your pattern of recurrences for two or more outbreaks before deciding whether to restart. Many people find their recurrence frequency has naturally declined over time.
References
- Patel R, et al. British Association for Sexual Health and HIV (BASHH). UK national guideline for the management of anogenital herpes. International Journal of STD & AIDS. 2024. doi:10.1177/09564624241282396
- Corey L, Wald A, Patel R, et al. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. New England Journal of Medicine. 2004;350(1):11--20. doi:10.1056/NEJMoa035144
- Looker KJ, et al. 2024 European guidelines for the management of genital herpes. Journal of the European Academy of Dermatology and Venereology. 2025. PMC11934026
- NHS. Aciclovir. nhs.uk/medicines/aciclovir
- World Health Organization. Recommendations for treatment of genital herpes simplex virus. NCBI Bookshelf. ncbi.nlm.nih.gov/books/NBK396233
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.