What it is

Vitamin D3 is the same form of vitamin D that your skin makes in sunlight. Your doctor prescribes the dose based on your blood test.

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How to take it

• Take it once a day with your main meal that contains some fat. Fat helps your body absorb vitamin D.³
• Take it every day, all year round. Vitamin D is a long-term treatment.
• Take the number of capsules written on your label. Your doctor changes your dose by changing the number of capsules.

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If you were given a loading bottle

• Take the loading bottle exactly as written on its label, until it is empty.
• Then move on to your second bottle, as written on its label. You don’t need to come to the clinic to make the change.
• Never take both bottles at the same time.

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If you miss a dose

Take it as soon as you remember. If it is nearly time for your next dose, skip the missed one. Do not take two doses to make up.²

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No withdrawal if you stop

Vitamin D stays in your body for weeks, so your level falls slowly. Missing doses, or stopping when your doctor advises, does not cause withdrawal symptoms. This also means your follow-up visit can be a little earlier or later than planned.⁴

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Please stop

• Any other vitamin D. Taking two products together can push your total dose too high.¹
• Calcium supplements. Get your calcium from food instead. Vitamin D helps your body absorb more calcium. A supplement adds a large amount at once on top of that, and this is one of the main reasons calcium in the blood rises too high in people taking vitamin D.⁵ Taking calcium supplements every day has also been linked with kidney stones and a higher risk of heart and blood vessel problems.^3,6,7 Food gives your bones the calcium they need, spread across your meals, without these risks. If a doctor prescribed calcium for osteoporosis, keep taking it.

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Tell us if you take

None of these means you cannot take vitamin D. Some medicines and vitamin D affect each other a little, so knowing what you take helps us look after you more closely.

• A statin, such as atorvastatin, lovastatin or simvastatin. Your liver uses the same enzyme for these statins and for vitamin D, so vitamin D may make the statin work slightly less well. Your doctor may keep a closer eye on your cholesterol.³
• A thiazide water pill. These pills keep more calcium in your body. Together with vitamin D, calcium can rise in some people, especially older adults or people whose kidneys work less well. You can still take vitamin D; we simply watch your calcium.³
• Rifampicin or isoniazid, which are tuberculosis medicines. They can make vitamin D work less well in your body, so we look at your results with this in mind.¹
• Liquid paraffin, a laxative. It can reduce how much vitamin D you absorb from your capsule.¹
• Warfarin or any other blood thinner. Many people take vitamin K2 with vitamin D. We will not give you vitamin K2 if you take a blood thinner, because vitamin K can change how well warfarin works, and there is not enough information yet about K2 with other blood thinners.⁸
• Any new medicine you start while taking vitamin D, so we can check that the two work well together.

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Contact us if you notice

These can be signs that the calcium in your blood is higher than it should be. Vitamin D helps your body absorb calcium, so too much vitamin D for too long can raise it. This is very rare in people who follow our plan, because we keep your dose within safe limits and check your blood regularly. We tell you so that you know what to look out for, as part of good care.⁹

• Feeling sick, or losing your appetite
• Constipation
• Passing urine a lot, or feeling very thirsty
• Unusual weakness or confusion

These usually have other causes. We will check your calcium to be sure. Go to a hospital the same day if you have severe confusion, are very drowsy, or keep vomiting.

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How to store it

• Keep it in its original bottle, away from light and moisture.
• Store it below 25°C, in a cool, dry place. You do not need to keep it in the fridge.
• Keep it out of the sight and reach of children.

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Calcium from food

We ask you to stop calcium supplements, so we want to make sure you still get enough calcium for your bones from what you eat. Vitamin D can only help your bones if there is calcium to absorb. This table helps you choose foods you enjoy and add them up across the day.

Most adults need 1,000–1,200 mg of calcium a day. Your body absorbs it best in amounts of no more than 500 mg at a time.¹⁰

• Calcium-fortified soy milk, 1 glass (200 ml): 368 mg calcium
• Small crispy fish, dried shrimp, 2 tablespoons: 357 mg calcium
• Canned sardines in oil (with bones), 85 g: 325 mg calcium
• Cow’s milk, 1 carton (250 ml): 300 mg calcium
• Dark leafy greens, such as Chinese kale, 1½ cups: 300 mg calcium
• Firm tofu (made with calcium sulphate), ½ cup: 253 mg calcium
• Plain yoghurt, 1 small cup (125 g): 200 mg calcium
• Canned salmon (with bones), 85 g: 181 mg calcium
• Boiled soybeans, ½ cup: 131 mg calcium
• Cooked spinach, ½ cup: 123 mg calcium

Tip: tofu is high in calcium only when it is made with a calcium salt. Cut down on tea, coffee, alcohol and very salty food.¹¹

Medically reviewed by Dr. Chontirot, MD · Medical licence no. 36583 · Last reviewed: 31 October 2026

References

1. Colonis Pharma Ltd. Colecalciferol 1,000 IU Capsules — Summary of Product Characteristics. emc, UK; 2021.

2. Colonis Pharma Ltd. Colecalciferol 1,000 IU Capsules — Package leaflet: Information for the patient. 2021.

3. National Institutes of Health, Office of Dietary Supplements. Vitamin D — Fact Sheet for Health Professionals. Updated 2025.

4. National Osteoporosis Society. Vitamin D and Bone Health: A Practical Clinical Guideline for Patient Management. 2018.

5. Burt LA, Billington EO, Rose MS, et al. Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial. JAMA. 2019;322(8):736–745.

6. Panay N, Fenton A, Hamoda H, et al. Recommendations and Key Messages on Women’s Midlife Health and Menopause (International Menopause Society). Climacteric. 2025.

7. Roeca C, Al-Safi Z, Santoro N. The Postmenopausal Women. In: Feingold KR, et al., editors. Endotext. MDText.com; updated 2025.

8. National Institutes of Health, Office of Dietary Supplements. Vitamin K — Fact Sheet for Health Professionals.

9. Goltzman D. Hypercalcemia. In: Feingold KR, et al., editors. Endotext. MDText.com; updated 2026.

10. National Institutes of Health, Office of Dietary Supplements. Calcium — Fact Sheet for Health Professionals. Updated 2026.

11. Swadpanich P. Examples of calcium-rich foods (in Thai). Faculty of Medicine Siriraj Hospital.

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