How to Get the Best Dosage of Aciclovir

Dr Kathryn Basford

Medically reviewed by

Dr Kathryn Basford

Last reviewed: 26 Feb 2019

Which dosages are used for which conditions

Woman checking the dosages of Aciclovir

Key takeaways

  • Aciclovir dosage changes depending on what and who it's being used to treat

  • 200mg or 400mg dosages are normally used for treating genital herpes and 400mg is used for cold sores

  • A doctor can check the right dosage for you. It be different for different people

  • You may need to switch your aciclovir dosage depending on your situation

  • There are things you can do to get the most out of your aciclovir dosage

There are different dosages of aciclovir available, depending on what condition you're using it for and what your personal circumstances are. Make sure you're confident in the dosage you need when you get treatment.

What dosages of aciclovir are available?

Treatment with aciclovir can be vary because:

  • There are lots of different dosages and these might need to change as part of your treatment, with dosages ranging from 100 mg to 800 mg or from 5 mg/kg to 10 mg/kg
  • There are lots of different types of formulas: eye ointments, creams, tablets and intravenously
  • How often you need to use Aciclovir per day or how many days for might vary

What exactly your treatment specifics are will be decided by your doctor when you’re assessed.

Some of the specific dosages for adults are below:

Local treatment – when you’re using a 'local' treatment of herpes infection it refers to either eye ointment or a skin cream. Usually, you’d use about 1 cm of the ointment for at least 3 days and as much cream as directed by your doctor for 5 to 10 days.

Suppression of herpes – the commonly prescribed dosage is 400 mg, twice a day, though this might need to be increased if there are recurrences. You might also be told to stop using it every 6–12 months so that your physician can reassess how often recurrence might occur

Genital herpes outbreaks:

  • If this is occurring for the first time, 400 mg taken 3 times a day will be used for 5 to 10 days. Longer doses might be needed for people who are HIV-positive or immunocompromised: you should speak to your doctor if this is the case
  • For recurrent infections, the dosage that is prescribed can either be 800mg (usually 2 x 400mg tablets) taken 3 times a day for 2 days, or 400mg taken 3 times a day for 5 days


  • When you’re taking tablets, usually 800 mg is prescribed to be taken 5 times a day for 7 days, even in those who are immunocompromised, or 10 mg/kg is recommended for intravenous use for 5 days
  • If you need to have intravenous infusion for 5 days, 5 mg/kg is given unless you’re immunocompromised; in that case, it’s 10 mg/kg

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What dosages are used for genital herpes and cold sores?

The dosage you’re prescribed is usually the same for either genital herpes or cold sores. 400mg is the strength of Aciclovir used for both but the number of tablets you take per day, and how long you take them for will be different depending on what’s being treated.

How do I find out the right dosage for me?

The right dosage depends on your personal situation – a doctor can let you know what the right dosage is for you, as this can be different depending on you as a person. The aim of the dosage is for it to have maximum efficacy but with less risk of side effects. How they decide will be based on some details like those below:

Weight – if you’re overweight, then you need to be dosed at the recommended dosages using Ideal Body Weight (IBW).

Age – if you’re elderly, then you’re more likely to have reduced liver function than when you’re younger, so you’ll need a lower dosage. There’s no concrete evidence that aciclovir is safe and effective in people younger than 2 years, so this isn’t recommended for them.

Health conditions and treatments – if you’re receiving treatment related to your liver or kidneys, you might need a specific treatment schedule.

You should tell your doctor if you’re taking any drugs, since these could interact with aciclovir. Some of the drugs include those used for:

  • HIV/AIDS – zidovudine
  • Bacterial or fungal infections – amphotericin B, foscarnet, gentamicin, kanamycin
  • Cancer – talimogene laherparepvec, cisplatin
  • Pain relief – Motrin, ibuprofen

When would you switch dosages?

It depends on your situation – it’s possible that you may need to switch your aciclovir dosage. Your doctor is likely to make this decision based on factors like those below:

  • Your response to the current dosage – if your symptoms are not properly controlled by your current dosage you could get assessed by a doctor in order to change to a stronger dosage
  • Starting new course of other medications – if you start to suffer from any other illnesses and need to start taking new medications for that, then you need to let your doctor know. This could impact how much of each drug you can take; it can be a balancing act and monitoring of your side effects might be necessary
  • What side effects you experience – for example, normally you’re prescribed a relatively high dosage of aciclovir for shingles, and this might mean that you have more severe side effects. These should be watched quite carefully, and if the side effects are too detrimental, then changes in the dosage might be recommended

How do you get the most effective aciclovir treatment?

There are a few things you can do to support your treatment – to get the best experience with your treatment, you should do your best with the following:

  • Start your medication as soon as you can after your symptoms start and take your medication as directed by your doctor
  • Timing your doses – it’s best to take Aciclovir as soon as possible after the first sign of any symptoms - so as soon as you notice the tingling or burning that you get before a cold sore or genital herpes blister
  • Food and drink – you can use your tablets, capsules and oral suspension with your meals or on an empty stomach, but one thing that could interfere is dehydration. If you’re taking any of these Aciclovir formulas, then you should drink plenty of water. This is particularly important if you’re elderly or taking doses of 400 mg a day or higher
  • Accuracy for measuring doses – if you need to measure out your dosages, you need to try and be accurate, for example if you’re using an aciclovir oral suspension. Using a specially marked measuring spoon or anything else similar and help you measure your dosages.
  • Completing your course – to help clear up your infection, you should always finish your full treatment, even if you’re not feeling your symptoms anymore. in a similar way, don’t take the medication for longer than you’ve been told to
Medically reviewed by:
Dr Kathryn Basford Accreditations: MB, ChB, MPH

Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with ZAVA. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.

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Last reviewed: 26 Feb 2019

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