The NHS is urging millions of people across the UK to take vitamin D to support overall health, but experts say certain symptoms should not be ignored. In a post shared on X, an NHS spokesperson 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.”While health professionals agree that vitamin D supplementation is important for many people, especially during the colder months, they stress that it should be taken carefully.Why Does Sunlight Matter For Vitamin D Production?Sunlight plays a crucial role in how the body makes vitamin D. UVB rays trigger a reaction in the skin that converts a compound called 7-dehydrocholesterol into vitamin D3. This form of vitamin D is essential for absorbing calcium, maintaining strong bones, and supporting the immune system.As sunlight in the UK is not strong enough between autumn and early spring, the government advises everyone to consider taking a daily supplement of 10 micrograms, or 400 IU. Relying on food alone is often not enough to meet daily needs during this period.Expert Warns Too Much Vitamin D Can BackfireBiomedical scientist Tobias Mapulanga, who co-founded Repose Healthcare, has warned that some people may be taking more vitamin D than their bodies can handle. He explained that as winter advice circulates, many people add tablets, sprays, or gummies without realising they are doubling up.He said that symptoms such as constant thirst, needing the toilet more often, nausea, stomach discomfort or constipation, headaches, mental fog, and new aches or cramps can appear soon after increasing vitamin D intake. These signs are often mistaken for winter illnesses, when they may actually point to excess supplementation.“The message is simple,” he added. “The right dose helps, but taking too much can leave you feeling worse, not better.”High-Dose Supplements Raise Safety ConcernsResearch shows that 42% of UK adults reported taking vitamin D supplements in the past year. However, an investigation by Which? found some vitamin D products on sale contained doses as high as 12.5 times the recommended safe upper limit.NHS England also logged 42 incidents over a two-year period where high-strength vitamin D was given more often than intended. Some of these cases led to hospital treatment for hypercalcaemia, a condition caused by too much calcium in the blood, according to reports from Bristol Live.Stop Taking Vitamin D If You Notice These Warning Signs1. Ongoing thirst and frequent trips to the toiletIf you suddenly feel unusually thirsty or find yourself urinating more often after starting vitamin D, it may be a sign you’re overdoing it. Cut back to a single 10 microgram tablet and stop using any additional vitamin D products if this happens.Too much vitamin D can disrupt fluid and salt balance in the body, leaving you dehydrated and running to the bathroom. Check labels carefully and remove multivitamins, sprays, gummies, and fortified foods or drinks that also contain vitamin D.Keep water close by and sip regularly while your body settles. Stay well below the upper limit of 100 micrograms, keep just one product visible, and put the rest out of sight to avoid accidental doubling.2. Nausea, excessive burping, or stomach discomfortFeeling sick, bloated, or dealing with an upset stomach after taking vitamin D suggests it isn’t agreeing with you. Try taking your supplement with a full meal and switch from sprays or gummies to a plain D3 tablet if symptoms persist.Food helps protect the stomach lining, while sprays and gummies often contain sweeteners or flavourings that can irritate digestion. Choose a simple cholecalciferol tablet with minimal ingredients and reduce the dose to 10 micrograms.Avoid fortified shakes or energy drinks until your stomach feels normal again.3. New muscle cramps or bone achesIf you notice more aches in your bones or frequent muscle cramps after starting vitamin D, take it as a signal to reassess. Lower your dose and focus on staying well hydrated while eating mineral-rich foods.Excess vitamin D can interfere with mineral balance, which muscles rely on, and dehydration can make cramping worse. Drink water with meals and include yoghurt, leafy greens, beans, and bananas in your diet.Gentle stretching and short walks can ease stiffness. Stick to one 10 microgram supplement and avoid adding anything else until symptoms improve.4. Brain fog or headachesTrouble concentrating or recurring headaches can be signs that your vitamin D intake is too high. Replace multivitamins or high-strength products with a single 10 microgram D3 tablet.High doses can raise calcium levels, and extra additives found in combined supplements may affect clarity of thought. Choose a product that contains only cholecalciferol and basic fillers.Take it with food at the same time each day for consistency and better digestion. Avoid combined vitamin A and D products and focus on one simple supplement.To prevent accidental overuse, review everything you take that contains vitamin D. Spread out all tablets, sprays, gummies, and fortified foods, and read each label carefully. Convert IU to micrograms by dividing by 40 to make totals easier to track.Discard any extras and stick to one daily 10 microgram source. Keep a note of symptoms such as thirst, frequent urination, stomach upset, cramps, or mental fog to see how they relate to your intake.