--- title: "Vitamin D Deficiency Is Rising in Teenagers and Young Adults: 9 Signs That Are Easy to Mistake for Tiredness" description: Vitamin D deficiency is rising in UK teenagers and young adults. The 9 signs to watch for, the blood test to ask for and how much to take in winter. author: Dr Marina Nani (Editor-in-Chief) date: 2026-11-06T12:00:00.172Z updated: 2026-11-06T12:00:00.187Z canonical: https://richhealthmagazine.com/article/vitamin-d-deficiency-symptoms image: https://cdn.nanimediahouse.com/pexels-6382594.webp categories: Food & Nutrition content_type: Guide publication: Rich Health Magazine schema_type: Article --- A 23-year-old teacher who played in goal four times a week collapsed at work this autumn. The blood tests that followed showed her vitamin D was close to zero. Her story, [reported by the BBC](https://www.bbc.co.uk/news/articles/cm78pxxe55v0o), is not rare. Nearly a quarter of 11 to 18 year olds in the UK are now classed as deficient, and nearly one in five adults aged 19 to 65 has low levels. The early signs are vague. Tiredness, aches and a run of colds look like an ordinary British winter, so deficiency often goes unnoticed for months while it softens your bones. From October to March, the sun in the UK is too weak for your skin to make the vitamin D you need. That makes now the time to check what you are getting. ## Vitamin D Deficiency in the UK Severe deficiency, a blood level below 25 nmol/L, is rising among teenagers, people from ethnic minority groups and pregnant women. Among adults aged 40 to 69, more than half have levels below 50 nmol/L, and in winter and spring that rises to around seven in ten. A group of UK doctors and nutrition scientists has called for the official threshold for deficiency to be doubled from 25 to 50 nmol/L, in line with many other countries. Their reasoning is that a higher bar would catch people earlier, before bones and muscles are affected. Vitamin D controls how much calcium and phosphate your body absorbs from food. Without enough, you can eat plenty of calcium and still fail to use it, and over time your bones lose strength. ## Signs of Low Vitamin D These are the symptoms the NHS and the British Heart Foundation list for low vitamin D and its adult bone condition, osteomalacia. - **Tiredness that does not lift.** Low vitamin D can leave you more tired than your sleep and workload explain. - **Catching more infections.** People with low levels tend to pick up colds and other infections more often. - **Aching bones.** Pain in your back, shoulders, ribs, pelvis or legs can come from bones that are softening. - **Swollen, painful wrists.** This is one of the classic signs of osteomalacia. - **Weak muscles.** You may find stairs harder, or struggle to get up from a low chair without pushing on your arms. - **Tingling, cramps or twitching.** Muscles can cramp or twitch when calcium levels fall. - **Tiring when you walk.** Some people walk less, change the way they walk or tire quickly on a short distance. - **Bones that break easily.** A fracture after a minor fall, especially in the hips, lower back or feet, can point to soft bones. - **Changes in children.** Bowed legs, slow growth and teeth arriving late are signs of rickets. Tiredness has many causes. Low iron is one of the most common in women, and our guide to [iron deficiency symptoms in women](https://richhealthmagazine.com/article/iron-deficiency-symptoms-women) covers the signs and the blood test to ask for. If fatigue and brain fog are your main problem, read our guide on [ways to prevent extreme fatigue](https://richhealthmagazine.com/article/brain-fog-fatigue-prevention). ## Who Is Most at Risk of Vitamin D Deficiency You are more likely to run low if you: - have brown or black skin, for example an African, African-Caribbean or South Asian background, as darker skin needs longer in the sun to make vitamin D - spend most of your time indoors, at a desk, at home or in a care home - cover most of your skin when you are outside - are pregnant or breastfeeding - are over 65 - are a teenager or young woman, the groups where deficiency is rising fastest ## The Vitamin D Blood Test There is no routine vitamin D screening in the UK. If you have symptoms, ask your GP. The blood test measures 25-hydroxyvitamin D, the main form in your blood. A level above 50 nmol/L is enough for most people. A level below 25 nmol/L puts you at risk of soft bones and weak muscles. If your level is low, your doctor may prescribe a higher dose for a short time to bring it back up. Take a high dose only under medical supervision. ## How Much Vitamin D to Take in Winter Government advice is that everyone aged 4 and over should consider a daily supplement of 10 micrograms (400 IU) from October to March. If you are at higher risk, take it all year round. You can read the full advice on dose in our guide to [who should take vitamin D and how much](https://richhealthmagazine.com/article/vitamin-d-winter-uk). Do not take more than 100 micrograms (4,000 IU) a day unless a doctor tells you to. Over time, too much vitamin D builds up calcium in your blood, which can damage your bones, kidneys and heart. You cannot overdose on vitamin D from sunlight. Vitamin D3 raises blood levels more effectively than D2. Most D3 is made from sheep's wool, so if you are vegan, look for a supplement labelled vegan or made from lichen, or choose D2. ## Foods High in Vitamin D Food alone rarely covers your winter needs, but these help: - **Oily fish.** A 140g portion of grilled mackerel gives you 11.9 micrograms and the same portion of baked salmon gives 10.2 micrograms. - **Eggs.** One boiled egg gives 1.6 micrograms. - **Vitamin D enriched mushrooms.** An 80g portion gives 3.2 micrograms. - **Fortified cereals and spreads.** A 30g bowl of fortified wheat biscuits gives 1.4 micrograms. - **Red meat and liver.** Both contain small amounts. Avoid liver if you are pregnant. Cows' milk in the UK is not fortified with vitamin D, unlike in some other countries, so a glass of milk will not help. From late March to September, 15 minutes outside without sunscreen two or three times a week lets most people make what they need, and longer if you have brown or black skin. Never stay out long enough to burn. ## Vitamin D Questions **Q: How much vitamin D per day should a woman take?** Women in the UK, including pregnant and breastfeeding women, need 10 micrograms (400 IU) of vitamin D a day. Government advice is to take a 10 microgram supplement daily from October to March, and all year round if you have darker skin, spend little time outdoors or cover your skin. Do not take more than 100 micrograms (4,000 IU) a day unless a doctor advises it. **Q: What strength vitamin D should I take?** For most adults, a daily supplement of 10 micrograms, also written as 400 IU, is enough. Higher doses are sometimes prescribed for a short time to treat a diagnosed deficiency, but these should only be taken under medical supervision. The safe upper limit for adults is 100 micrograms (4,000 IU) a day. **Q: What is the difference between vitamin D and vitamin D3?** Vitamin D is the name for a group of compounds. The two main forms in supplements are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). D3 is the form your skin makes in sunlight and raises blood levels more effectively. D3 is usually made from sheep's wool, so D2 or lichen-based D3 suits vegans. **Q: What are the symptoms of low vitamin D?** Low vitamin D can cause tiredness, more frequent infections, aching bones, muscle weakness, cramps and bones that break more easily. In children it can cause rickets, with bowed legs and slow growth. A blood test from your GP can confirm whether your levels are low.