Vitamin D / Colecalciferol (High Strength)

IMPORTANT — HIGH-DOSE VITAMIN D: SunVit-D3 10,000 IU (250 mcg) is a high-strength prescription vitamin D product. It is 25 times the standard NHS recommended daily supplement dose of 400 IU. It is prescribed for confirmed vitamin D deficiency and must not be taken without a valid prescription. This dose is used under medical supervision for the treatment of confirmed vitamin D deficiency. Taking this dose without medical supervision can cause vitamin D toxicity (hypervitaminosis D) and raised blood calcium (hypercalcaemia). Blood calcium and vitamin D levels require monitoring during and after treatment. This product must not be taken without a valid prescription.

Vitamin D deficiency is a common medical condition in the UK, particularly among older adults, those with limited sun exposure, and certain population groups. When deficiency is confirmed through blood testing, a loading course of high-dose vitamin D is often required to restore levels to the normal range before beginning maintenance supplementation. Colecalciferol 10,000 IU (250 mcg) is a Prescription Only Medicine used for this purpose under medical supervision. A prescription can only be issued following a clinical consultation.

Colecalciferol is the pharmaceutical name for vitamin D3, the form of vitamin D most closely resembling that produced naturally in the skin when it is exposed to ultraviolet B sunlight. Colecalciferol 10,000 IU is a high-strength prescription formulation of vitamin D3, providing 250 micrograms (mcg) per dose. This is a therapeutic dose used for the treatment of confirmed vitamin D deficiency and is not a daily supplement product.

For comparison, the NHS recommends a standard daily supplement dose of 10 mcg (400 IU) of vitamin D for all adults to maintain vitamin D status. The 10,000 IU dose is 25 times this amount. It is used in a loading course to rapidly replenish vitamin D stores when blood levels are confirmed to be deficient (typically defined as a serum 25-hydroxyvitamin D level below 25 to 30 nmol/L, though local laboratory reference ranges vary). After completing the loading course, patients are usually maintained on a lower daily dose.

Licensed products containing colecalciferol 10,000 IU in the UK include Stexerol-D3 10,000 IU tablets. Generic colecalciferol 10,000 IU products from other manufacturers may also be available. All contain the same active ingredient and should only be used under medical supervision.

Colecalciferol 10,000 IU works through the same mechanism as lower-dose vitamin D supplements, but at a therapeutic level that rapidly replenishes depleted vitamin D stores.

Activation and Mechanism

After oral administration, colecalciferol is absorbed from the gut in the presence of dietary fat. It is then converted in the liver to 25-hydroxyvitamin D (calcidiol), the main circulating storage form of vitamin D measured in blood tests. In the kidneys, 25-hydroxyvitamin D is further converted to the active hormone 1,25-dihydroxyvitamin D (calcitriol), which binds to vitamin D receptors throughout the body.

Bone Health and Calcium Absorption

The primary clinical indication for vitamin D supplementation is the maintenance of normal calcium and phosphorus metabolism for bone health. Vitamin D contributes to the normal absorption of calcium from the intestine. Without adequate vitamin D, calcium absorption falls significantly and the body withdraws calcium from bones to maintain blood calcium levels. Confirmed vitamin D deficiency can lead to osteomalacia (bone softening) in adults, bone pain, muscle weakness, and increased fracture risk. A therapeutic loading course corrects the deficiency and allows bone health to be supported going forward.

Immune Support and Muscle Function

Vitamin D receptors are present throughout the immune system, and adequate vitamin D status is associated with supporting normal immune function. Vitamin D also contributes to normal muscle function. Both of these physiological roles are clinically relevant in deficiency states, where immune function and muscle strength may be impaired. Correcting vitamin D deficiency through a supervised loading course supports the restoration of these normal functions as part of overall clinical management.

Always take colecalciferol exactly as your prescriber instructs. The dosing regimen for 10,000 IU colecalciferol is prescribed on an individual basis depending on the severity of deficiency, the patient's age, body weight, and the presence of conditions affecting vitamin D metabolism. The information below reflects general clinical practice based on current UK guidelines; your prescriber's specific instructions always take precedence.

• Take each dose with food containing some fat to maximise colecalciferol absorption.
• Swallow the tablet or capsule whole with a glass of water.
• A typical loading regimen for vitamin D deficiency in adults consists of several weekly or fortnightly doses totalling approximately 300,000 IU over several weeks, achieved using 10,000 IU doses taken daily or weekly over the prescribed period, followed by maintenance therapy. Your prescriber will specify the exact number of doses and frequency.
• Do not take additional vitamin D supplements (including over-the-counter products or multivitamins containing vitamin D) without telling your prescriber, as this may push your total intake above safe levels.
• Attend all blood monitoring appointments requested by your prescriber. Blood calcium and vitamin D levels should be checked during and after the loading course.
• Do not extend the loading course beyond the period prescribed. Once loading is complete, you will typically be switched to a lower maintenance dose.
• Contact your prescriber or seek medical advice if you experience symptoms that could indicate raised blood calcium, including nausea, vomiting, constipation, excessive thirst, frequent urination, muscle weakness, or confusion.

SunVit-D3 10,000 IU: Prescribing Regimen

Colecalciferol 10,000 IU is used as part of a loading regimen to correct confirmed vitamin D deficiency. The total loading dose recommended in UK clinical guidelines (NICE, ROS, RCGP) is typically in the range of 300,000 IU over 6 to 10 weeks for adults with confirmed deficiency. This is usually achieved by taking 10,000 IU doses weekly or fortnightly over this period. The exact regimen is determined by the prescriber based on the patient's blood results and individual clinical circumstances.

Following the loading course, vitamin D status is reassessed with a blood test. Maintenance therapy is then initiated at a lower daily dose, typically 800 to 2,000 IU (20 to 50 mcg) per day, which can be obtained from lower-dose prescription or over-the-counter products. The 10,000 IU loading dose is not intended for indefinite daily use.

Special Populations

In patients with conditions that affect calcium or vitamin D metabolism, such as sarcoidosis, primary hyperparathyroidism, or granulomatous conditions, vitamin D supplementation must be managed with particular caution as these patients are at increased risk of hypercalcaemia. Colecalciferol loading doses should be prescribed by a specialist in these patients. In patients with renal impairment, dose adjustment and close monitoring are required as the kidneys are involved in vitamin D activation.

When used at the prescribed dose under medical supervision, colecalciferol 10,000 IU is safe for most patients. The principal risk is vitamin D toxicity (hypervitaminosis D), which causes raised blood calcium (hypercalcaemia).

Signs of Hypercalcaemia: Seek Medical Advice Promptly

Contact your prescriber or seek medical advice if you experience any of the following during or after a colecalciferol loading course:

• Nausea, vomiting, or loss of appetite.
• Constipation.
• Excessive thirst or dry mouth.
• Passing urine more frequently than usual.
• Muscle weakness or aches.
• Headache.
• Confusion or difficulty concentrating.
• Kidney stones (severe back or flank pain).

These symptoms may indicate raised blood calcium and require urgent medical assessment.

Contraindications

Colecalciferol 10,000 IU must not be used in patients with:

• Hypercalcaemia (raised blood calcium) or hypercalciuria (raised calcium in the urine).
• Renal calculi (kidney stones containing calcium).
• Known hypersensitivity to colecalciferol or any excipient.
• Conditions associated with elevated calcium metabolism such as sarcoidosis, unless under specialist supervision.

Tell your prescriber and pharmacist about all medicines you take before starting colecalciferol 10,000 IU.

• Thiazide diuretics (such as bendroflumethiazide): combined use with vitamin D increases the risk of hypercalcaemia. Calcium and vitamin D levels should be monitored.
• Digoxin: hypercalcaemia can increase the risk of digoxin toxicity. Monitor carefully if both are prescribed.
• Orlistat: reduces the absorption of fat soluble vitamins including colecalciferol. Doses may need to be separated.
• Antiepileptic medicines (phenytoin, phenobarbitone): may reduce vitamin D effectiveness by accelerating its metabolism.

This Medicine May Be Appropriate If You:

• Have confirmed vitamin D deficiency on a blood test, with a serum 25-hydroxyvitamin D level indicating deficiency per your local laboratory reference range.
• Have been assessed by a prescriber who has determined that a loading course is clinically appropriate for your individual circumstances.
• Do not have contraindications including hypercalcaemia, hypercalciuria, renal calculi, or relevant hypersensitivity.

This Medicine Is Contraindicated If You Have:

• Hypercalcaemia or hypercalciuria.
• A history of renal calculi associated with hypercalciuria or hyperuricosuria.
• Sarcoidosis or other granulomatous disease, unless under specialist supervision.
• Known hypersensitivity to colecalciferol or any ingredient in the product.

Requires Extra Caution In:

• Patients with renal impairment. Dose reduction and closer monitoring are needed.
• Patients taking thiazide diuretics or digoxin.
• Patients with primary hyperparathyroidism.
• Patients taking antiepileptic medicines.

Colecalciferol 10,000 IU is a Prescription Only Medicine. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber concludes, based on their individual assessment of your circumstances, that a loading course of high-dose colecalciferol is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review the information you provide. This includes your blood test results confirming vitamin D deficiency, current medicines, relevant medical history, and any conditions that may affect calcium or vitamin D metabolism. Recent blood test results showing your 25-hydroxyvitamin D level will be required before a loading prescription can be issued.

Not all consultations will result in a prescription. The prescriber may request more recent blood test results, recommend a lower maintenance dose product if deficiency is borderline rather than confirmed or advise that specialist involvement is needed. This process is designed to protect your safety.

Blood calcium and vitamin D levels must be monitored during and after the loading course. Your prescriber will advise on the appropriate follow-up blood tests and timing. Pharmacy Planet will support you through this monitoring process and can arrange follow-up consultations to review your results and prescribe maintenance therapy once the loading course is complete.

Store below 25°C in a dry place. Store in the original packaging, away from light and moisture. Keep out of the sight and reach of children. High dose vitamin D can cause serious harm to children if taken accidentally. Do not use after the expiry date printed on the packaging. Do not dispose of medicines via household waste or wastewater. Return unused or out of date product to your pharmacist for safe disposal. Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

Pharmacy Planet is a GPhC registered online pharmacy providing access to prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, clinical accuracy, and responsible prescribing. For high-dose prescription vitamin D products such as colecalciferol 10,000 IU, our prescribers review blood test results before prescribing, check for relevant contraindications and drug interactions, and arrange appropriate monitoring follow-up. Every prescription is reviewed and dispensed by qualified healthcare professionals. If you have questions about vitamin D deficiency, the loading regimen, or your blood test results, our pharmacy team is available to help. We are committed to transparent, patient centred care.

References

1. Electronic Medicines Compendium (eMC). Stexerol-D3 10,000 IU tablets — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed May 2026.
2. National Institute for Health and Care Excellence (NICE). Vitamin D deficiency in adults — treatment and prevention. NICE guideline. https://cks.nice.org.uk/topics/vitamin-d-deficiency-in-adults. Accessed May 2026.
3. NHS. Vitamin D. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d. Accessed May 2026.
4. Joint Formulary Committee. British National Formulary (BNF). Colecalciferol. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed May 2026.
5. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed May 2026.

Vitamin D Products

The table below compares the two vitamin D products in the Vitamins range. Both contain cholecalciferol (vitamin D3) but differ fundamentally in dose, classification, and intended use.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.