Skip to main content


vitamin D

Clinical author's note Michael Stewart 05/12/2022: AT10® oral drops were discontinued in the United Kingdom in January 2021. At the time of review there are no branded or generic products containing dihydrotachysterol available in the UK. Dihydrotachysterol may still be available in other countries. Other forms of vitamin D are available. This medicine leaflet is based on medical information available in the UK at the time of writing and is left here for reference purposes. Please also refer to the manufacturer's information supplied with your medicine.

Dihydrotachysterol is a type of vitamin D. It helps your body absorb calcium.

Make sure you understand how much to take and when to take it.

You will need to have regular blood tests while you are taking this medicine so that your doctor can make sure the dose is right for you.

Make sure you know the symptoms of too much calcium in your blood - these are losing your appetite, feeling thirsty, being sick (vomiting), feeling tired, and losing weight. See your doctor if you develop these symptoms.

Continue reading below

About dihydrotachysterol

Type of medicine

A type of vitamin D

Used for

Low blood calcium levels due to hypoparathyroidism

Also called

AT10® (discontinued)

Available as

Oral solution (drops)

Dihydrotachysterol is a form of vitamin D. Vitamin D helps you to absorb calcium from the foods you eat. You need calcium to keep your bones strong, and to help your muscles and nerves work properly. If you have a low level of calcium in your blood, it can cause a number of different symptoms, including muscle cramps, pain and twitching. Low levels of calcium can be caused by a problem with your parathyroid glands, called hypoparathyroidism. Dihydrotachysterol is used to treat low blood levels of calcium when caused by hypoparathyroidism.

Before taking dihydrotachysterol

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking dihydrotachysterol it is important that your doctor knows:

  • If you are allergic to peanuts or soya. If so, you must not take this medicine.

  • If you are pregnant or breastfeeding.

  • If you have sarcoidosis. This is a condition causing inflammation, particularly in your lungs and lymph system. Sarcoidosis may make you more sensitive to dihydrotachysterol than normal.

  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

Continue reading below

How to take dihydrotachysterol

  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The leaflet will give you more information about dihydrotachysterol and a full list of side-effects which you may experience from taking it.

  • Take dihydrotachysterol exactly as your doctor tells you to. It is likely you will be asked to take 3-5 ml for the first three days, and then your dose will be adjusted depending on the results of a blood test. You could then be asked to take a dose each day, on alternate days, or several times a week. Your doctor will tell you what is right for you, and how much to take for each of your doses.

  • Make sure you understand how to measure out your doses using the dropper. You can ask your doctor, nurse or pharmacist to explain this to you again if you are uncertain.

  • You can take dihydrotachysterol before or after meals.

  • If you forget to take a dose, take it as soon as you remember unless it is nearly time for your next dose, in which case leave out the missed dose. Do not take two doses together to make up for a forgotten dose.

Getting the most from your treatment

  • Keep your regular doctor's appointments so your progress can be monitored. You will need to have regular blood tests while you are taking this medicine to make sure that the dose you are taking is correct for you.

  • You should consider wearing a MedicAlert® bracelet (or similar), or carry some kind of ID with you, to identify yourself as having hypoparathyroidism. This is so that if you collapse, are confused or are injured, doctors will know that you need prompt treatment with calcium.

  • Eating foods rich in vitamin D and calcium may help, such as oily fish (sardine, herring, salmon and tuna), liver, dairy products and eggs.

  • If you buy any medicines, check with a pharmacist that they are suitable for you to take with dihydrotachysterol.

  • Treatment with dihydrotachysterol is usually long-term. Continue to take it regularly unless you are advised otherwise by your doctor.

  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking dihydrotachysterol.

Continue reading below

Can dihydrotachysterol cause problems?

Along with their useful effects, medicines can cause unwanted side-effects although not everyone experiences them. Any side-effects caused by dihydrotachysterol are likely to be due to too much calcium in your blood, which means that your dose will need adjusting.

The first signs of too much calcium are:

  • Loss of appetite.

  • Tiredness.

  • Feeling sick (nausea).

This could then lead on to:

  • Being sick (vomiting).

  • Stomach cramps.

  • Feeling thirsty.

  • Needing to pass urine more often.

  • Sweating.

  • Dizziness.

  • Headache.

If you experience these symptoms, it is important that you make an appointment to see your doctor straightaway.

How to store dihydrotachysterol

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

  • Keep the bottle tightly closed and store in the original carton to protect it from light.

  • Discard any remaining contents four months after first opening the bottle. Write the date of opening on the label to remind you.

Important information about all medicines

Important information about all medicines

Never take more than the prescribed dose. If you suspect that you or someone else has taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

symptom checker

Feeling unwell?

Assess your symptoms online for free