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Reviewed on Jan 16, 2026. byDr Alexandra Cristina CowellWriter & Clinical Content ReviewerRegistered with GPhC (No. 2241935)Next review due on January 16, 2029.
Last updated on Jan 16, 2026.
Product info
Vitamin D supplement available in three strengths.
Low-strength doses to maintain levels, and high-strength doses for severe deficiencies.
Veggie, vegan, halal, and kosher-friendly treatment. It’s also lactose and gluten free.
Price checker
400 IU
800 IU
1000 IU
£29.95
30 Capsule(s)£29.95
90 Capsule(s)£43.95Save £45.90
Prices include:
Express shipping
24 hour shipping by secure courier.
Consultation + Access to our clinicians
Ask our experts anything you like, any time you want.
Pro D3 is one of a number of vitamin D supplements and treatments that can be used to treat and prevent severe deficiencies from occurring. It comes in capsule and liquid forms, as well as different strengths, depending on why it’s being taken.
We get most of our vitamin D from the sun, or at least we should. But unfortunately, this isn’t always easy during the winter months. This is particularly a problem for people with darker skin, which does not process vitamin D from the sun as efficiently as those with lighter skin.
Supplements are a great solution, and Pro D3 offers various strengths to provide protection against severe deficiencies that can lead to serious conditions like osteoporosis. Prescription strengths are available to treat deficiencies, as well as lower doses to top up your levels.
How does Pro D3 work?
Pro D3 works by increasing the amount of vitamin D in your body, thanks to its main ingredient – colecalciferol, which your body processes and converts into the active form of vitamin D.
Vitamin D is an important part of healthy body function, and it can:
Maintain good calcium levels, giving you stronger bones
Ensure good function of the immune system
Help to prevent tiredness and fatigue
Support your mental health[1][2]
What doses of Pro D3 are there?
Pro D3 capsules are available in 5 different ‘maintenance’ doses, ranging from 400 to 2,500 IU (IU is the measurement by which supplement strength is measured) and 2 different treatment doses: 20,000 and 30,000 IU. We only supply the 400mg, 800mg, and 1000mg strengths
A maintenance dosage might be needed to slightly increase your levels of vitamin D, in which case a product like Pro D3 1000 IU would be suitable.
The higher strength doses that are prescribed to treat severe deficiencies will need to take into account just how severe your vitamin D levels are. One of the most commonly prescribed products is Pro D3 20,000 IU, but be sure to talk to your clinician to make sure you’re getting the right dose
Treated trusted sources:
Aranow, C. (2011). Vitamin D and the immune system. Journal of investigative medicine: the official publication of the American Federation for Clinical Research, 59(6), pp.881–6.
Naeem, Z. (2010). Vitamin d deficiency- an ignored epidemic. International journal of health sciences, 4(1), pp.V–VI.
This page was written by The Treated Content Team.
This page was medically reviewed by Dr Alexandra Cristina Cowell on January 16, 2026. Next review due on January 16, 2029.
How we source info.
When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.
Pro D3Colecalciferol
How to take Pro D3
Pro D3, in either capsule or liquid form, is best taken with a meal as this helps the body get the most out of the treatment. For Pro D3 liquid, shake the bottle before use. You can add it to water or food. Pro D3 capsules should be swallowed whole with water.
The maintenance doses are to be taken daily, unless you’re told otherwise by your prescriber. And as for treatment doses, always follow your clinician’s instructions. Typically, the 20,000 IU capsules are taken twice a week (or two 20,000 IU once a week) for seven weeks. The 30,000 IU capsules are taken once a week for ten weeks in total. Treatment doses are usually followed by an ongoing maintenance dose that is taken daily.
How long does it take Pro D3 to work?
If you are suffering from a vitamin D deficiency, then it can take some weeks or months before your vitamin D levels are back up to a recommended level, depending on your current levels.[3] Whereas if you are just taking the maintenance strength supplement to maintain good levels of vitamin D in your body, then the results will be immediate (in that your body should continue to perform as it should).
What should I do if I make a mistake when taking Pro D3?
Pro D3 should be safe to take in most ways, the only concern could be if you take a lot more than you’ve been advised to, as this can cause some serious issues.
Hypercalcaemia, in particular, can be dangerous and will need medical attention if you notice any of its symptoms. These include: digestive problems, severe fatigue, palpitations, disorientation, excessive thirst and needing to urinate frequently.
If you accidentally miss a dose, it shouldn’t usually be a problem. Just make sure that you don’t try to double the next dose to make up for it.
This page was written by The Treated Content Team.
This page was medically reviewed by Dr Alexandra Cristina Cowell on January 16, 2026. Next review due on January 16, 2029.
How we source info.
When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.
Pro D3Colecalciferol
Pro D3 isn’t suitable for everyone, and there are some things that you need to be aware of when taking it.
Here’s all the official info on it. If anything is unclear, let our clinician know, and they can talk with you about it.
Pro D3Colecalciferol
FAQ: Pro D3
Have something specific you want to know? Search our info below, or ask our experts a question if you can’t find what you’re looking for.
How is Pro D3 different from other vitamin D supplements?
Answer:
Pro D3 is halal and vegetarian friendly, as well as being lactose and gluten free - which not all vitamin D supplements are - so make sure you choose a vitamin D supplement that suits your needs.
Is Pro D3 similar to any other vitamin D supplements?
Answer:
Aside from the branding, price and some ingredients, Pro D3 is similar to most vitamin D supplements that use vitamin D3. This is because vitamin D3 is considered the most easy for your body to process.[1] As a result, all vitamin D supplements and treatments will generally work in the same way to keep you healthy.
What you will need to make sure you get right is the dosage, and that you choose the version and ingredients that suit you.
Which version and dose of Pro D3 should I use?
Answer:
The dose of Pro D3 that you should take will depend on your current levels of vitamin D and the advice of our clinician. If you are suffering from significant vitamin D deficiency, then you will be better suited to the higher dose treatment. But if you simply want to maintain your vitamin D health, then one of the lower strength daily supplements will suit you better.
The version of Pro D3 that you should use will be down to your own personal preference. Pro D3 is available as both a capsule and a liquid, so have a think about what you’d prefer, and if it’s not working then you can always switch to an alternative later on.
Do I need a prescription for Pro D3?
Answer:
For some vitamin D products, you will need a prescription. This is because high levels of vitamin D can cause serious health problems, so they aren’t always suitable for everyone. These dosages are only prescribed when you have a severe vitamin D deficiency, treating related conditions, such as osteoporosis.
In the case of Pro D3, for the lower doses up to 2,000 IU you don’t need a prescription. But for the higher doses of 20,000 and 30,000 IU you do need a prescription from your clinician.
Treated trusted sources:
Tripkovic, L, Et al. 2012. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. The American journal of Clinical Nutrition. USA. NCBI.
Last updated on Jan 16, 2026.
How we reviewed this page:
Our experts continually monitor new findings in health and medicine, and we update our articles when new info becomes available.
Why this page was updated on Jan 16, 2026
Content checked and updated as part of our 3-yearly periodic review, to ensure accuracy and currentness.
Current version (Jan 16, 2026)
Edited by: The Treated Content Team.Medically reviewed by: Dr Alexandra Cristina Cowell, Writer & Clinical Content Reviewer
Jan 03, 2023
Published by: The Treated Content Team.Medically reviewed by: Dr Daniel Atkinson, GP Clinical Lead
How we source info.
When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.
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When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.
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