The NHS has recorded multiple incidents of serious illness and consumer experts have issued their own alert
10:44, 20 Jan 2026Updated 11:07, 20 Jan 2026
Millions of people take vitamins every day(Image: )
The NHS is urging millions of people to take vitamin D to help with their health, but an expert has warned you need to look out for some red flag side effects. Posting on X, an NHS spokesman said: “From October to March we can’t make enough vitamin D from sunlight, so to keep bones and muscles healthy, it’s best to take a daily 10 microgram supplement of vitamin D. You can get vitamin D from most pharmacies and retailers.”
And while experts agree many people in the UK should be taking vitamin D , especially through the winter, the advice comes with a note of caution.
People need sunlight to get vitamin D because UVB rays from the sun trigger a chemical reaction in the skin. This process converts 7-dehydrocholesterol into vitamin D3, which is important for calcium absorption, bone health, and immune system support.
The UK government recommends that everyone consider taking a daily vitamin D supplement of 10 micrograms (400 IU) during the autumn and winter months because sunlight isn’t strong enough for bodies to make enough vitamin D, and it’s tough to get enough from food alone.
Tobias Mapulanga, biomedical scientist and co-founder of Repose Healthcare, has warned of symptoms you need to watch for. He said: “As the NHS encourages vitamin D in winter, many people are reaching for bottles in the darker months and accidentally overshooting, then blaming the fallout on seasonal bugs; when constant thirst and needing the loo more often, queasiness, tummy pain or constipation, headaches or brain fog, and new aches or cramps appear soon after increasing your intake or adding sprays or gummies, that points to a supplement backfiring. The stakes are clear: the right amount supports you, but doubling up can turn a well-meant routine into feeling worse rather than better.”
42% of surveyed UK adults had taken vitamin D supplements within the last 12 months but Which? found supplements, including vitamin D, for sale with doses up to 12.5 times the recommended safe upper limit. NHS England identified 42 reports over two years of high‑strength vitamin D being given more frequently than intended, with some cases needing hospital treatment for hypercalcaemia.
Stop taking your vitamin D supplement if you spot these red flags:
1. Frequent thirst and urination
If you find that you are now frequently thirsty and/or urinating more after you start taking vitamin D, it is a signal that you may be taking too much. Cut intake to a single 10 microgram tablet and drop any extras if these symptoms appear. Excess vitamin D can disrupt fluid and salt balance, leaving you parched and visiting the loo more. Check food or drink labels and remove multis, sprays, gummies and fortified drinks or cereals with added D. Keep water close and sip as the body settles. Stay well under the 100 microgram upper limit while symptoms persist, keep one product by the kettle and store the rest out of sight.
2. You feel nausea, constant burping or a sour stomach
Feeling a sense of nausea, burping more or a sour stomach after you’ve taken vitam D is another sign things aren’t right. Try to take your supplement with a main meal and switch from sprays or gummies to a simple D3 tablet if symptoms kick in. Food buffers the supplement in the gut and reduces irritation, while sprays and gummies often contain sweeteners or flavourings that upset some people. Choose a plain cholecalciferol tablet with minimal fillers and step the dose back to 10 micrograms. Avoid fortified shakes or energy drinks while the stomach settles.
3. Your bones and muscles hurt
If you find that your bones ache more or that your muscles are cramping more frequently when you start your vitamin D supplement, it’s a flag. Scale back and prioritise fluids and mineral‑rich foods. Excess vitamin D can disturb the minerals muscles rely on, and dehydration makes cramping more likely. Drink a large glass of water with meals and include yoghurt, leafy greens, beans and bananas throughout the day. Gentle stretching and a short walk help ease tightness. Return to a single 10 microgram dose and skip any extras while symptoms settle.
4. You can’t think straight
Brain fog and headaches are a sure flag that your vitamin D intake is too much. Swap any multi or high‑strength product for a plain 10 microgram D3 tablet. High doses can push calcium levels up, and additives in multis can muddle thinking. Choose a product listing only cholecalciferol and simple bulking agents. Take it with food at the same time each day to keep intake steady and gentler on the gut. Leave combined A+D products on the shelf and focus on one simple D3 tablet. Pick a small tablet to make consistency effortless.
5. Too many products with Vitamin D
Pay attention to how many products you’re consuming that contain vitamin D, because an overdose is possible when you are unaware. Audit all sources and pick one daily product to avoid overlaps from tablets, multis, sprays, gummies and fortified foods. Lay out everything containing vitamin D and read each label carefully. Convert IU to micrograms by dividing by 40 so totals are clear at a glance. Drop duplicates and keep only one 10 microgram source. Jot down dose and any thirst, frequent urination, tummy upset, cramps or brain fog to spot links with intake.
