Cialis vs Viagra – Which is Best?

Price, dosage, effects, and side effects. Here’s everything you need to know about two of the most popular erectile dysfunction treatments

Pack of Cialis vs Viagra
Contents of this article

You may have heard of both Cialis and Viagra, but not known which one to try. Or maybe you’re looking to switch from one to the other.

Cialis and Viagra can both work very well, but they have some important differences that might affect which one is the best choice for you.

What are the key differences between Cialis and Viagra?

What are the active ingredients?

  • Cialis contains the active ingredient ‘tadalafil
  • Viagra contains the active ingredient ‘sildenafil

How easy are they to buy?

  • Viagra has been available in the UK for much longer than Cialis
  • Since March 2018, there has also been Viagra Connect, available to buy in the UK. This is the 50mg dosage of Viagra. It’s an over-the-counter version of Cialis, which means you don’t need a prescription for it
  • Sildenafil (in Viagra) can be prescribed freely on the NHS, but Cialis and tadalafil are still restricted

Do I need a prescription?

  • Cialis can only be bought with a prescription
  • Viagra can also only be bought with a prescription
  • But Viagra Connect is available to buy over the counter, without a prescription

How well do they work?

  • They work almost equally well as each other. But the number of people Viagra works for is slightly higher at 84%, compared to around 81% for Cialis
  • Food doesn’t affect how Cialis works
  • Viagra can work less well if you’ve eaten recently, especially if it was a meal that’s high in fat

How long they work for

  • The effects of Cialis last for longer – up to 36 hours
  • The effects of Viagra last for 4 to 5 hours
  • Cialis often works well for over the weekend, and it’s sometimes called the ‘weekend pill’, because its effects last for up to 36 hours

The dosages they come in

  • Cialis is available in four different dosages: 2.5mg, 5mg, 10mg and 20mg
  • Viagra comes in three dosages: 25mg, 50mg or 100mg

How they’re taken

  • The 2.5mg and 5mg dosages of Cialis are taken every day. They are called 'Cialis Daily'. They can work well for people who want to get an erection more than once a week, or people who don't want to plan before they need an erection
  • The 10mg and 20mg dosages of Cialis are taken ‘on-demand’, before each time you want to get an erection
  • Viagra is also taken on-demand, before each time you want to get an erection

Side effects

  • There isn’t much difference between the most common side effects of Cialis and Viagra
  • Cialis side effects may be more likely, and harder to put up with, as it lasts so much longer than Viagra
  • For this same reason, Cialis may be more likely to interact with other medications you may be taking. This could cause side effects in itself. If you’re taking certain medications, particularly medications called alpha-blockers (e.g. doxazosin, tamsulosin or alfuzosin) this can cause a dangerous drop in your blood pressure, so Cialis may not be recommended for you

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What are the similarities between Cialis and Viagra?

What they are and how they work

  • They’re both called ‘PDE5-inhibitors’ and they work in the same way
  • Each of them can be used as a ‘first-line’ treatment for most forms of erectile dysfunction (ED)
  • They’re both available in their cheaper generic versions. For Cialis, this is tadalafil. For Viagra, this is sildenafil
  • They’re usually prescribed at a lower dosage at first. This can be increased if lower dosages don’t work
  • They can cause similar side effects
  • They’re both available to purchase online, but a doctor still needs to confirm your suitability before giving a prescription online

Taking Cialis and Viagra

  • They’re taken between 30 minutes to 1 hour before sex (except for Cialis daily dosages)
  • If you’re taking Cialis or Viagra, you should also make lifestyle changes to help manage your ED. These changes could include quitting smoking or losing weight, as well as seeing your GP to look into any physical causes you may have
  • Cialis and Viagra both require sexual stimulation to work. They don’t increase your sexual desire
  • Each one may need to be taken a few times on separate occasions before it starts to work
  • Sometimes a doctor won’t prescribe a treatment if some of your health details might make it unsafe. With Cialis and Viagra, these types of health details are very similar, because they both work in a similar way
  • Both can be misused. If you’re getting Cialis or Viagra online, you should always use an online pharmacy that’s regulated by the General Pharmaceutical Council (GPhC) and the Care Quality Commission (CCQ)

Why is Viagra more well-known than Cialis?

Viagra was invented first. Both are popular treatments for erectile dysfunction (ED) but Viagra has been around since 1998. Cialis has been available since 2003 in the UK.

Sildenafil, which is the generic version of Viagra, has also been available longer than either Cialis or tadalafil.

The size of Pfizer as a company also helps to explain why Viagra is so well known. Eli Lilly, the company that makes Cialis, is much smaller.

Can I try both?

Yes, but not at the same time. They’re designed to be taken at a maximum of one dosage, once a day.

Serious side effects are rare if you take your treatment correctly as prescribed by your doctor. But there are serious risks to taking them together, including a higher chance of experiencing these side effects:

  • Heart attack
  • Stroke
  • Seizures
  • Loss of vision
  • Loss of hearing
  • Severe skin reactions
  • Severe allergic reactions
  • Priapism. This is an erection that lasts for longer than 4 hours, or is painful

If you experience any of these side effects, you should get medical attention from your nearest A&E as soon as possible.

Which should I try first?

This will depend on your personal preference, as well as whether you’re suitable for each treatment.

After trying one, you could carry on with the same treatment or switch to another, depending on your personal experience.

When should I switch?

It might be worth switching if you find that one’s more effective and causes fewer side effects. Some people find that the first or second dosage works. Others may respond after a few more attempts on different occasions.

If you find it’s not working for you after around 8 different attempts, speak to your online doctor or GP to consider another option.

Can I buy both together?

Yes, you can try our erectile dysfunction trial pack to test out which one is best for you.

How can I tell which one is right for me?

The best way to know which one is right for you is to try each of them for yourself.

How will I know it's working?

With either Cialis or Viagra, you’ll know it’s working if you notice that your erections are firmer and last longer. This may take a few tries.

How will I know if either one is right for me?

Getting an assessment done by an online doctor or your GP will tell you whether you’re suitable for treatment. This usually involves providing information about your general health, like your weight, as well as any current medical conditions, like diabetes or high blood pressure.

How would I decide on the right one?

Deciding which one is best for you could depend on a few things:

  • How long you want the effects to last for
  • Whether you’d prefer a daily pill, or one that you take as needed, before each time you want to get an erection
  • How many times a week you want to get an erection
  • If one of the treatments gives you side effects that impact your life

To help you make the best decision and compare which one is better, you could:

  • record your experiences as you try each one  
  • try taking each one separately, but keep other details the same so you can clearly see the difference between treatments
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