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How to Take Aciclovir Tablets: Complete Guide

Published on: June 03, 2026

Understanding how to take aciclovir tablets correctly can significantly improve treatment outcomes for cold sores. At Cured Pharmacy, our UK-registered clinical team has guided thousands of patients through effective aciclovir therapy, and this comprehensive guide shares the essential administration advice that ensures optimal results.

Understanding Aciclovir: How It Works Against Cold Sores

Aciclovir is an antiviral medication that works by interfering with the replication of the herpes simplex virus (HSV-1), the primary cause of cold sores [1]. Once absorbed, aciclovir is converted by viral enzymes into its active form, which then blocks the viral DNA polymerase enzyme essential for HSV replication.

Clinical studies demonstrate that aciclovir can reduce healing time by an average of 1-2 days when started at the first sign of cold sore symptoms, such as tingling or itching around the lips [2]. The medication is most effective when initiated within 48 hours of symptom onset, though it may still provide benefit if started later during an outbreak.

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has licensed aciclovir for both treatment and suppression of recurrent herpes simplex infections. Treatment typically involves higher doses over shorter periods, whilst suppressive therapy uses lower daily doses for patients experiencing frequent outbreaks.

Standard Aciclovir Dosage for Cold Sores

For treating active cold sore outbreaks, the standard UK prescription dose is 200mg taken five times daily for five days [3]. This frequent dosing schedule maintains therapeutic blood levels throughout the day, maximising antiviral activity during the critical replication phase of the virus.

An alternative dosing regimen of 400mg three times daily for five days is also licensed and may be more convenient for some patients, offering similar clinical efficacy with fewer daily doses [3]. Your UK prescriber will determine which regimen suits your lifestyle and medical history following your online consultation.

Higher-Dose Regimens

Some prescribers may recommend 800mg aciclovir five times daily for immunocompromised patients or those with severe outbreaks. This higher dose ensures adequate antiviral coverage in individuals whose immune systems may not respond as effectively to standard therapy. All prescription medications at Cured Pharmacy require clinical assessment by a UK-registered prescriber to ensure appropriate dosing for your individual circumstances.

How to Take Aciclovir Tablets Correctly: Step-by-Step Instructions

Aciclovir tablets should be swallowed whole with a full glass of water. The medication can be taken with or without food, though taking it with meals may help reduce potential stomach upset in sensitive individuals [4]. Consistency in timing is more important than whether you take it with food.

For the five-times-daily regimen, space doses approximately four hours apart during waking hours. A practical schedule might be 7am, 11am, 3pm, 7pm, and 11pm. For the three-times-daily regimen, aim for roughly eight-hour intervals, such as 8am, 4pm, and midnight.

Never double up on doses if you miss one. If you remember within an hour or two of the scheduled time, take the missed dose immediately. If it's nearly time for your next dose, skip the missed one and continue with your regular schedule. Maintaining adequate hydration throughout treatment is important, as aciclovir is processed through the kidneys.

Starting Treatment at the Right Time

The prodromal phase—that characteristic tingling, itching, or burning sensation before visible blisters appear—is the optimal window to begin aciclovir therapy. Research shows that starting treatment during this early stage can sometimes prevent the cold sore from fully developing or significantly reduce its severity [2]. Keep aciclovir tablets readily available if you experience frequent outbreaks, so you can begin treatment immediately when symptoms start.

Product Form Typical Dosing Starting Price
Aciclovir Tablets 200mg Oral tablet 5 times daily for 5 days From £19.99
Aciclovir Tablets 400mg Oral tablet 3 times daily for 5 days From £19.99
Numark Cold Sore Cream Topical cream (5% aciclovir) 5 times daily for 5 days From £4.49

Common Side Effects and How to Manage Them

Aciclovir tablets are generally well-tolerated, with most patients experiencing no side effects. When adverse effects do occur, they're typically mild and transient. The most commonly reported side effects include headache, nausea, diarrhoea, and abdominal discomfort [4].

Rare but more serious side effects can include dizziness, confusion, or signs of kidney problems such as reduced urine output. These are more likely in elderly patients or those with pre-existing kidney conditions. If you experience severe headache, unusual bruising, yellowing of skin or eyes, or difficulty breathing, seek immediate medical attention.

To minimise side effects, ensure you drink plenty of water throughout your treatment course—aim for at least 6-8 glasses daily. This supports kidney function and helps prevent crystallisation of the medication in the urinary tract, a rare complication associated with inadequate hydration during aciclovir therapy.

Aciclovir Tablets vs Aciclovir Cream: Which Is More Effective?

Both oral aciclovir tablets and topical aciclovir cream are licensed for cold sore treatment in the UK, but they work through different mechanisms and offer distinct advantages. Oral tablets provide systemic antiviral coverage, meaning the medication circulates throughout your bloodstream and reaches the site of viral replication from within.

Clinical evidence suggests that oral aciclovir is generally more effective than topical cream for treating cold sores, particularly for reducing healing time and symptom severity [1][2]. Topical aciclovir cream, such as the Numark Cold Sore Cream available at Cured Pharmacy from £4.49, is applied directly to the cold sore five times daily and may be suitable for mild outbreaks or as an additional therapy.

Tablets are particularly advantageous for patients experiencing frequent or severe outbreaks, those who catch infections early in the prodromal phase, or individuals who prefer the convenience of systemic treatment. Topical cream may be preferred by those who experience only occasional, mild cold sores or who wish to avoid oral medication.

Combination Therapy Approach

Some patients find that combining oral aciclovir tablets with topical cream provides enhanced symptom relief, though clinical evidence for additive benefit is limited. If considering this approach, consult with your prescriber during your online consultation at Cured Pharmacy to ensure it's appropriate for your situation.

For patients experiencing six or more cold sore outbreaks per year, suppressive aciclovir therapy may be recommended. This involves taking a lower dose—typically 400mg twice daily—continuously for 6-12 months [3]. Clinical trials demonstrate that suppressive therapy can reduce outbreak frequency by 70-80% in patients with recurrent herpes simplex infections.

Suppressive therapy is particularly beneficial for individuals whose quality of life is significantly impacted by frequent cold sores, those with outbreaks triggered by predictable events (such as sun exposure or stress), or immunocompromised patients at higher risk of severe infections. Your UK prescriber will assess whether this approach is suitable based on your outbreak history and overall health status.

At Cured Pharmacy, our clinical team can review your medical history during a free online consultation to determine whether episodic treatment or suppressive therapy is the most appropriate strategy for managing your cold sores. All aciclovir prescriptions are subject to clinical assessment by a UK-registered prescriber, ensuring you receive personalised care tailored to your specific circumstances.

Scientific References

  1. Spruance, S. L., et al. (1997). Peroral famciclovir in the treatment of experimental ultraviolet radiation-induced herpes simplex labialis: a double-blind, dose-ranging, placebo-controlled, multicenter trial. Journal of Infectious Diseases, 175(5), 1071-1077. https://doi.org/10.1086/516445 [accessed 13 August 2026]
  2. Spruance, S. L., et al. (2003). High-dose, short-duration, early valacyclovir therapy for episodic treatment of cold sores: results of two randomized, placebo-controlled, multicenter studies. Antimicrobial Agents and Chemotherapy, 47(3), 1072-1080. https://doi.org/10.1128/AAC.47.3.1072-1080.2003 [accessed 13 August 2026]
  3. British National Formulary. (2024). Aciclovir: Medicinal forms. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk/drugs/aciclovir/ [accessed 13 August 2026]
  4. Electronic Medicines Compendium. (2023). Aciclovir 200mg and 400mg Tablets - Summary of Product Characteristics. Datapharm Ltd. https://www.medicines.org.uk/emc/ [accessed 13 August 2026]

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication.

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Faq

How quickly does aciclovir work for cold sores?
Aciclovir typically begins reducing viral replication within hours of the first dose, though visible improvement may take 1-2 days. Clinical trials show that starting treatment during the prodromal phase can reduce healing time by an average of 1-2 days compared to no treatment.
Can I drink alcohol whilst taking aciclovir tablets?
There is no direct interaction between aciclovir and alcohol, so moderate alcohol consumption is generally considered safe. However, alcohol may worsen side effects such as dizziness or nausea, and may compromise your immune response during an active outbreak.
Should I take aciclovir with or without food?
Aciclovir can be taken with or without food—absorption is not significantly affected by meals. Taking it with food may help reduce stomach upset in sensitive individuals, but the most important factor is maintaining consistent timing between doses.
What happens if I miss a dose of aciclovir?
If you miss a dose and remember within 1-2 hours, take it immediately. If it's nearly time for your next scheduled dose, skip the missed one and continue with your regular schedule—never double up on doses to compensate.
How long should I take aciclovir tablets for cold sores?
The standard treatment course is five days, even if symptoms improve earlier. Completing the full course ensures adequate viral suppression and may reduce the risk of prolonged or recurrent outbreaks. Your prescriber may adjust the duration based on your response to treatment.
Can I use aciclovir tablets to prevent cold sores?
Yes, suppressive aciclovir therapy (typically 400mg twice daily) can reduce outbreak frequency by 70-80% in patients experiencing frequent recurrences. This approach requires ongoing prescription and monitoring by a UK prescriber, available through Cured Pharmacy's online consultation service.
Is aciclovir safe during pregnancy?
Aciclovir is generally considered safe during pregnancy when clinically necessary, as extensive use has not revealed significant risks. However, all medication use during pregnancy should be discussed with your prescriber, who will weigh the benefits against any potential risks for your specific situation.
Do I need a prescription for aciclovir tablets in the UK?
Yes, aciclovir tablets are prescription-only medication in the UK and require clinical assessment by a UK-registered prescriber. At Cured Pharmacy, you can complete a free online consultation in under three minutes to determine if aciclovir is appropriate for your cold sore treatment.
Is aciclovir available without a prescription in the UK?
No, aciclovir tablets require a prescription in the UK. At Cured Pharmacy, our UK-registered pharmacists can issue prescriptions following a free online consultation, making it convenient to access treatment without visiting your GP.
How much does aciclovir cost at Cured Pharmacy?
Aciclovir tablets at Cured Pharmacy start from competitive prices that include your free consultation and prescription service. The exact cost depends on the strength and quantity prescribed following your assessment by our pharmacists.
How quickly can I get aciclovir tablets delivered in the UK?
Cured Pharmacy offers next-day discreet delivery across the UK when you order before our cut-off time. All aciclovir orders are dispatched in plain, unmarked packaging to protect your privacy.
Can I take aciclovir tablets long term for recurrent outbreaks?
Yes, aciclovir can be taken long term as suppressive therapy for frequent recurrent herpes infections. Our pharmacists at Cured Pharmacy can assess whether long-term daily aciclovir treatment is suitable for your individual circumstances during your consultation.
What is the difference between aciclovir and valaciclovir tablets?
Valaciclovir is converted to aciclovir in the body but requires less frequent dosing due to better absorption. Both are effective antiviral treatments, and Cured Pharmacy can help you determine which option suits your lifestyle and treatment needs best.
Tarun Kumar, Prescribing Pharmacist

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Reviewed on: June 03, 2026

Last reviewed: 13 August 2026

Last updated on 13 August 2026.

Review History

Our experts continually monitor new findings in health and medicine, and we update our articles when new information becomes available.

Why this page was updated on 13 August 2026

Content checked and updated as part of our periodic review, to ensure accuracy and currentness.

Current version (13 August 2026)

Edited by: The Editorial Team

Medically reviewed by:

Tarun Kumar, GPhC No. 2233073, Prescribing Pharmacist


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