Experts Warn Of Vitamin D Overdose Risks This Winter

As the winter sun fades across the United Kingdom, millions of people dutifully reach for their vitamin D supplements, heeding public health advice to ward off the risks of deficiency. Yet, in a twist that’s caught many by surprise, health experts are now warning that this well-intentioned routine can quietly turn against you—sometimes with serious consequences.

The NHS has long encouraged Brits to take a daily 10 microgram (400 IU) vitamin D supplement from October to March, when weak sunlight leaves most residents unable to generate enough of the nutrient naturally. The advice is grounded in science: vitamin D is crucial for bone strength, muscle function, and immune support, and a lack of it can lead to bone deformities in children and painful conditions like osteomalacia in adults. According to a study cited by LADbible, about half of UK adults have low vitamin D levels, and one in six reports taking supplements.

But as more people embrace supplements, a new concern has emerged. Biomedical scientist Tobias Mapulanga, co-founder of Repose Healthcare, sounded the alarm on January 23, 2026, cautioning that, "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." Mapulanga’s stark warning, reported by The Mirror and echoed in The Evening Standard, underscores a paradox: the right amount of vitamin D supports health, but too much can make you feel worse rather than better.

This isn’t just theoretical. Consumer group Which? discovered that some vitamin D products on UK shelves contain doses up to 12.5 times the recommended safety threshold. NHS England logged 42 incidents over two years in which high-strength vitamin D was administered more frequently than intended, with some cases requiring hospital treatment for hypercalcaemia—a dangerous condition where calcium levels in the blood soar, potentially harming the heart, kidneys, and bones.

So, what are the warning signs that you might be getting too much of a good thing? Experts have identified four key symptoms that should prompt anyone taking vitamin D to stop and reassess:

1. Persistent Thirst and Frequent Urination
One of the earliest and most telling signs of vitamin D overdose is a sudden, unquenchable thirst coupled with more frequent trips to the bathroom. As Mapulanga explains, excessive vitamin D intake can disrupt the body’s fluid and salt balance, leaving you constantly parched and dashing to the loo. If this happens, experts recommend cutting back to a single 10 microgram daily dose and checking all your supplements, foods, and drinks for hidden sources of vitamin D.

2. Nausea, Burping, or Stomach Upset
Feeling queasy, suffering from persistent burping, or experiencing stomach discomfort after starting a new supplement? According to IBTimes, these digestive symptoms are your body’s way of signaling a problem. Sprays and gummies are often culprits, as they may contain sweeteners and additives that irritate the gut. “Try taking your supplement with a proper meal and switch from sprays or gummies to a simple D3 tablet if troubles persist,” Mapulanga advised in The Mirror.

3. Bone and Muscle Aches
It’s a cruel irony: vitamin D is supposed to help your bones and muscles, but too much can do the opposite. If you notice new or worsening aches, cramps, or stiffness, it could be a sign of mineral imbalance brought on by excess vitamin D. Experts advise hydrating well, eating mineral-rich foods like yoghurt and bananas, and scaling back to the recommended dose until symptoms subside.

4. Brain Fog and Headaches
Struggling to think straight, or suffering from headaches after popping your vitamin D? Elevated calcium levels caused by overdose can cloud your thinking and trigger pounding headaches. The advice here is to avoid multivitamins and high-strength supplements, opting instead for a straightforward 10 microgram D3 tablet taken with food at the same time each day.

How do people end up in this predicament? According to IBTimes and The Evening Standard, overdose rarely happens from a single supplement. Instead, it’s the result of "stacking"—taking multiple products containing vitamin D, from multivitamins to sprays, gummies, and even fortified foods. Confusion over labeling, with both micrograms and international units (IU) in play, can make it tough to track total intake. "It is very easy to take too much vitamin D without realising, so it’s important to check all sources and select just one daily item to prevent doubling up," The Evening Standard reported, echoing NHS guidance.

Jana Abelovska, a former Superintendent Pharmacist at Click Pharmacy, told Surrey Live that taking vitamin D with healthy fats, like nuts or yoghurt, can help with absorption, since the vitamin is fat-soluble. But she also warned, "Don't take too much vitamin D. Because it's a fat-soluble vitamin, it can build up in your body easier than other vitamins. Taking too much vitamin D long term can lead to hypercalcemia, an excess of calcium in the body, which can cause problems with your heart, kidneys and bones."

What’s the official line? The NHS and government health experts agree: adults, including pregnant and breastfeeding women, the elderly, and children aged 11 to 17, should not exceed 100 micrograms per day. For most, 10 micrograms daily is both safe and effective during the months when sunlight is scarce. Between late March and the end of September, most people can make all the vitamin D they need through sunlight and a balanced diet, so supplements may not be necessary.

For those who do take supplements, vigilance is key. NHS England recommends checking the labels of all products you consume, including cereals, drinks, and multivitamins, to avoid accidental doubling up. If any of the warning symptoms appear, the advice is clear: return to a single 10 microgram daily dose, take supplements with food, stay hydrated, and consult a doctor if symptoms persist.

Ultimately, while vitamin D remains a cornerstone of winter wellness for many in the UK, the message from health authorities is unmistakable—more is not always better. Paying close attention to subtle warning signs and supplement labels can prevent a good habit from quietly becoming a health hazard.