Thorens is a medication that comes in the form of 10 000 I.U. oral drops. I.U. stands for International Units and is the measurement used for vitamins and some medicines. Thorens is a vitamin supplement that is used to help increase the body’s production of vitamin D it usually gets through exposure to sunlight. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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Thorens is a liquid form of vitamin D3 that is taken as drops. This medication is suitable for people with, or at risk of a vitamin D deficiency. It can also be used to treat weak bone conditions such as osteoporosis and rickets. Babies, children, teenagers and adults can take Thorens. 

What is Thorens? 

Thorens is a medication that comes in the form of 10 000 I.U. oral drops. I.U. stands for International Units and is the measurement used for vitamins and some medicines. Thorens is a vitamin supplement that is used to help increase the body’s production of vitamin D it usually gets through exposure to sunlight. The active ingredient in Thorens is colecalciferol.  

The remainder of this article refers to vitamin D, indicating vitamin D3 (contained in Thorens) which is derived from animals (usually sheep’s wool). Thorens does not contain vitamin D2, which is derived from plants. 

Vitamin D helps the body to absorb calcium and we need it for strong bones, an active brain, healthy teeth and to support the immune system.  

Vitamin D is absorbed by the body through exposure to sunlight, however, people living in northern hemisphere countries do not always receive enough sunlight during the winter months. It is also important to note that excessive exposure to sunlight is not recommended as a way to obtain vitamin D due to the risk of skin cancer. 

Thorens can be taken as a vitamin D deficiency supplement for diseases caused by a lack of vitamin D (such as osteoporosis, rickets and osteomalacia) and general vitamin D deficiency.  

There are certain groups of people that are more likely to have vitamin D deficiency.  

These include: 

  • Older people – as we get older our body’s ability to produce vitamin D slows down; 
  • People who have limited exposure to the sun; 
  • People with darker skin – these people have more melanin in their skin which reduces its ability to produce vitamin D; 
  • Obese people; 
  • People with fat malabsorption; 
  • Breastfed babies – a mother’s breast milk does not contain a baby’s adequate vitamin D requirements.  

Anyone in these groups should consult a doctor before taking vitamin D. 

If you think you have a vitamin D deficiency you should ask your doctor for a test. 

When is Thorens used? 

Thorens oral drops are used when a person is diagnosed as having a vitamin D deficiency or a disease that affects the bones such as osteoporosis or rickets. 

Osteoporosis causes the bones to become fragile and more likely to break. As we age our bones become weaker, and osteoporosis speeds this up. This condition is common in women after the menopause, but can also affect men, younger women and children. A vitamin D supplement such as Thorens can help strengthen the bones and keep them healthy. Whilst Thorens cannot completely treat osteoporosis it can help prevent it for people who are at risk of this bone-weakening disease. 

Rickets affects the development of bones in children. It causes poor bone growth, brittle bones and pain. A vitamin D deficiency or lack of calcium can cause rickets in children. There is an adult form of rickets, known as osteomalacia. A vitamin D supplement, such as Thorens can treat and prevent rickets. 

Thorens is also used to regulate the immune system. We need a healthy immune system for our body to fight infection. 

There is also some evidence to show that vitamin D can help develop a healthy brain and the central nervous system. 

If you are diagnosed with a vitamin D deficiency it could be because you do not get enough exposure to sunlight. This can happen to people who live in countries where there is limited sunlight during the winter months. It is common for people who do not spend a lot of time outdoors. In these days of modern technology and children tending to spend more time indoors playing computer games vitamin D deficiency is a concern. It can also occur in people who are housebound or in care homes. 

There are some foods (but few) that contain vitamin D, either naturally or in a fortified form (when vitamin D is added to the original product). The most common of these are: 

  • Oily fish; 
  • Egg yolks; 
  • Red meat; 
  • Liver; 
  • Fortified milk (not common in the UK); 
  • Breakfast cereals;  
  • Fat spreads, such as margarine; 
  • Yogurt. 

Not all these foods contain natural vitamin D, so if you want to increase your intake you should check on the packaging whether a product is fortified. 

How do you use Thorens? 

Before taking Vit D, you should consult your doctor who can assess whether you need replacement and the specific dose. 

The body absorbs Thorens better if it is taken with a large meal. It can either be swallowed orally as drops during a meal or mixed with food. It should only be mixed with food when given to children, not taken as drops on their own.  

Depending on the age of the child you can mix the drops with a small amount of their food or milk. Do not put the drops into a container of milk or drink in case the child does not drink the whole amount, which means they will not have received the correct dose.  

Before use shake the container. Then use the pipette to extract the liquid and take the recommended number of drops. These can be taken directly into the mouth or mixed with food.  

This medication tastes like mild olive oil as it’s base is refined olive oil. 

What dosages are there? 

The dosage will depend on a person’s individual circumstances. One drop of Thorens contains 200 I.U. of vitamin D. The typical doses are: 


  • Babies aged 0-1 year – 2 drops per day; 
  • Children aged 1-18 years – 2-3 drops per day; 
  • Adults over 18 years – 3-4 drops per day. 

Treatment of deficiency 

  • Babies and children aged 0-18 years – 10 drops per day for 6 weeks then 2-5 drops per day for as long as advised by a doctor; 
  • Adults – 3-4 drops per day. 

The above are typical doses for the prevention and treatment of vitamin D deficiency and may be altered by your doctor. Dosages for osteoporosis and other conditions will be advised by your doctor as sometimes more is required.  

What are the side effects of Thorens? 

As with all medication, Thorens can have side effects, although not everyone will have them. Different medicines can affect people in different ways. The possible side effects (which are uncommon) are: 

  • Hypercalcaemia - a high level of calcium in the blood that can weaken bones, cause kidneys stones and affect the function of the heart and lung due to calcium deposits; 
  • Hypercalciuria – a high level of calcium in the urine which can cause kidney stones. 
  • If too much vitamin D is taken it can build up in the body over time and cause toxic symptoms. This may take several months or years to occur.  

When shouldn’t you use Thorens? 

Thorens drops may not be suitable for everyone. You should not use them if you: 

  • Are allergic to any of the ingredients in this medication (refer to package leaflet); 
  • Are allergic to vitamin D; 
  • Have high levels of calcium in your blood (hypercalcaemia) or urine (hypercalciuria); 
  • Suffer from kidney stones or a kidney disorder; 
  • Have high levels of vitamin D in your blood (hypervitaminosis D); 
  • Have an immune system disorder linked to vitamin D; 
  • Are undergoing heart-related therapy; 
  • Eat food enriched with vitamin D;  
  • Take calcium supplements; 
  • Take any other form of vitamin D. 

It is also advisable not to use Thorens if you are likely to be exposed to excessive sunlight.  

If you are pregnant, planning to become pregnant or breastfeeding you should talk to a doctor before taking Thorens drops. 

Thorens drops are unlikely to affect your ability to drive or operate machinery. 

Alcohol should not interact with Thorens drops. 

Does Thorens interact with other medication? 

It is important to tell your doctor or pharmacist if you are taking other medication before taking Thorens drops, including any herbal medicines. 

Thorens can interact with the following, or they can reduce its level of absorption into the body: 

  • Medicines containing vitamin D; 
  • Food rich in vitamin D; 
  • Certain heart medication; 
  • Certain kidney medication; 
  • Some cancer treatment medicines; 
  • Some steroids; 
  • Epilepsy medicines; 
  • Medicines to lower cholesterol levels; 
  • Weight loss medicines; 
  • Certain laxatives. 

If you are taking any of the above medication you should discuss this with your doctor before starting to take Thorens drops. If you take other medication it is preferable to take it at a different time from Thorens, either several hours before or after taking it. 

Where can you buy Thorens? 

Thorens is not an over-the-counter medicine, you must have a prescription from a doctor for it. You should have a blood test first to test your vitamin D levels. 

Can I get Thorens without a prescription?  

No, you can only get Thorens with a prescription. 


Cholecalciferol (vitamin D3) February, 2015. Retrieved 26 November, 2019 from 

DeNoon, D.J. The Truth About Vitamin D: What Kind of Vitamin D is Best? December 17, 2009. Retrieved 26 November, 2019 from 

CEReBRUM Dana Foundation. Vitamin D and the Brain: More Good News. Shytle, R.D., Bickford, P.C. April 7, 2009. Retrieved 26 November, 2019 from 

Henderson, R. Dr. July 18, 2019. What is vitamin D deficiency and should you take supplements? Retrieved November 26, 2019 from 

Overview. Osteoporosis. June 18, 2019. Retrieved 26 November, 2019 from 

Overview - Rickets and osteomalacia. May 25, 2018. Retrieved 26 November, 2019 from 

Package leaflet: Information for the user THORENS 10 000 I.U. /ml oral drops, solution 

The VitaminD Society. (N.D.). Retrieved 26 November, 2019 from 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.