Super Strength Vitamin D3 for Winter Immune Strength

Vitamin D contributes to the normal function of the immune system and to the maintenance of normal bones, teeth and muscle function. Reviewers most often take it for winter and immune support, as well as general bone health.

4000iu (100µg) is our highest everyday strength, chosen by customers who want strong support or have been advised a higher dose. It's within the recognised daily upper level for adults, but if you're unsure which strength suits you, we also offer 400iu and 1000iu, and you can always check with your GP.

Not quite, Vitamin D is the family name, and D3 (cholecalciferol) is the form most naturally produced by the body from sunlight and used in supplements like this one. D3 is generally considered the better-absorbed form, which is why it's the standard choice for everyday supplementation.

Many customers take the higher strength through the darker months; others prefer it year-round. UK guidance suggests considering a Vitamin D supplement in autumn and winter, when sunlight exposure is limited and the body makes less of its own.

Yes, Vitamin D, Calcium and K2 are common bone-health pairings, each contributing to normal bone maintenance in their own way. If you'd prefer them together, we also offer a combined D3 4000iu + K2 tablet as a simpler one-a-day option.

Vitamin D3 contributes to the maintenance of normal teeth as an authorised claim, working alongside Calcium and other nutrients that support the teeth's structure. It doesn't act alone, so a balanced diet remains important for overall dental health.

Reviewers often mention low mood and tiredness during darker months as reasons they started taking Vitamin D3, alongside wanting extra support for bones and immunity. Everyone's needs differ, so if you're concerned about your levels, it's best to speak with your GP.

Persistent tiredness is one of the most common reasons people reach for vitamin D3. Vitamin D contributes to normal function of the immune system and to normal muscle function, both of which affect how energetic you feel day to day. If you spend most of your time indoors or cover up outside, your levels may be low. This 4000iu strength gives steady daily support. If tiredness continues, ask your GP for a simple test.

Vitamin D status is best checked with a simple test rather than judged by how you feel day to day. Ask your GP if you'd like your level tested, especially if you're taking a higher-strength product like this one.

Taking more than recommended long-term can occasionally cause nausea, reduced appetite, thirst, tiredness or needing the toilet more often. 4000iu sits within the recognised daily upper level for adults, but if you're combining supplements or unsure, check with your GP or pharmacist first.

You can track your order using the link in your shipping confirmation email or by visiting your account page. UK standard delivery typically takes 2, 3 working days from dispatch. For international deliveries, please see our Shipping and Returns. If you need any further assistance, our Customer Care team is here to help at ask@justvitamins.co.uk.

UK standard delivery usually takes 2, 3 working days from dispatch (excluding weekends and bank holidays). For Next Day Delivery, please place your order by 1pm Monday, Friday for delivery on the next working day. You'll receive a tracking email as soon as your order has been dispatched, so we recommend checking your tracking information first if your order hasn't yet arrived.

If your order has not yet been dispatched, we'll do our best to help. Please contact our Customer Care team as soon as possible via email or live chat. Once an order has been dispatched, we're unfortunately unable to make changes or cancel it.

Yes. You can pause, skip, reschedule or cancel your subscription by logging into your account. Simply select Account at the top of the website and make any changes up to 3 days before your next scheduled dispatch.

We primarily serve customers in the UK, but we also deliver to selected international destinations. Please see our Shipping and Returns for the countries we currently ship to and applicable delivery charges.

We offer a 90-day hassle-free returns policy on unopened products. Return postage costs are the customer's responsibility unless the item is faulty or sent in error.

Our supplements are made in the UK in GMP-certified facilities to stringent quality standards. We carefully select our ingredients and carry out rigorous quality checks throughout the manufacturing process, so every product meets our high standards.

Every order is covered by our 90-day money-back guarantee. If you are not completely happy for any reason, contact our Customer Care team within 90 days of purchase and we will refund you, no awkward questions. It is our way of making it easy to try something new with confidence.