Key Takeaways
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Vitamin D is called the sunshine vitamin, yet it is low in many Indians. As winter begins and air quality worsens, it often drops further. Many people then ask whether their tiredness, body ache or rising blood sugar could be linked to it.
This guide explains the symptoms, why winter matters, how much we know about the link with diabetes and heart health and what you can do.
Tired, aching or worried about your vitamin D? Get a proper assessment.
What Does Vitamin D Do?
Vitamin D helps your gut absorb calcium and phosphorus, which keeps bones and teeth strong. It also supports muscle function and plays a part in the immune system. Your skin makes most of it when it is exposed to UVB rays from sunlight. A smaller amount comes from food and supplements.
Vitamin D Deficiency Symptoms
Symptoms of vitamin D deficiency include tiredness, bone pain and muscle weakness, although many people have no noticeable symptoms. Common signs in adults include persistent fatigue, aching in the back or legs, muscle cramps and difficulty climbing stairs. Some people also experience low mood or frequent aches.
| In children Severe deficiency can cause rickets, leading to soft bones and bowed legs. In adults, it can cause osteomalacia, which softens the bones and increases the risk of fractures. |
These symptoms can have other causes too, including anaemia, thyroid problems and vitamin B12 deficiency. A blood test can help determine whether your vitamin D levels are low.
How Common Is Low Vitamin D in India?
You may think living in a sunny country like India means you get enough vitamin D. But that is not always the case. You can spend most of your day indoors or cover most of your skin when you go outside. Both can affect how much vitamin D your body makes.
A 2024 study by Sreenivasulu et al. looked at 9,931 vitamin D tests from a hospital in Jodhpur, Rajasthan. The findings were:
- 60% of adults had vitamin D levels below 20 ng/mL.
- 24% of adults had levels between 20 and 29 ng/mL.
- Only 16% of adults had sufficient vitamin D levels.
The study also found that vitamin D deficiency was more common in women than in men. These figures come from hospital test records, so they may not reflect the whole Indian population.
Why Can You Have Low Vitamin D Even in India?
Your body makes vitamin D when your skin is exposed to sunlight. However, several everyday habits and other factors can affect how much vitamin D you get.
Spending most of your day indoors
If you work in an office or stay indoors for long hours, your skin may not get enough sunlight to make vitamin D.
Having darker skin
Melanin gives your skin its colour. Higher melanin levels can slow vitamin D production, so you may need more sunlight exposure than someone with lighter skin.
| Clinical Insight “In my clinical practice, I often remind patients that living in a sunny country does not guarantee adequate vitamin D levels. Your daily routine, time spent outdoors and diet all make a difference. If you have persistent tiredness, bone pain or muscle weakness, speak to your doctor about whether a vitamin D test is needed. Avoid taking high-dose supplements without medical advice.” Dr. Gurudatta Amin, BAMS, MD, PGDEMS, 19+ Years of Clinical Experience, CMO, Madhavbaug |
Keeping most of your skin covered
If your clothes cover your arms and legs, less skin is exposed to sunlight.
Using sunscreen
Sunscreen reduces the UVB rays that reach your skin. These rays help your body make vitamin D.
Not getting enough vitamin D from food
Few foods naturally contain vitamin D. If your diet is mostly vegetarian, you may get less unless you include fortified foods or other suitable sources.
Living in an area with air pollution
Pollution can block some of the UVB rays your skin needs to make vitamin D.
Even if you live in a sunny city, your vitamin D levels can still be low. If you often feel tired or have unexplained bone pain or muscle weakness, speak to your doctor about whether a vitamin D test is appropriate. These symptoms can have other causes, so testing can help you understand what your body needs.
Why Vitamin D Levels Fall in Winter
Your vitamin D levels can drop during winter, even if you live in a sunny part of India. This happens because your body depends on sunlight to make vitamin D, and you may get less of it during the colder months.
A study by Sreenivasulu et al. (2024), which examined vitamin D test results from a hospital in Jodhpur, found that the median vitamin D level was around 18.7 ng/mL during summer and the monsoon. In winter and spring, it fell to 15.8 ng/mL. Levels were highest in August and September and lowest during winter.
What Causes Vitamin D Levels to Drop in Winter?
A few seasonal changes can affect how much vitamin D your body makes.
| Reason | How it affects vitamin D levels |
| Less effective sunlight | During winter, the sun sits lower in the sky. Its UVB rays travel through more of the atmosphere, so fewer reach your skin. This effect is more noticeable in northern parts of India. |
| Less time outdoors | Shorter days and colder weather may mean you spend more time indoors. If you leave for work early and return after sunset, you may get very little sunlight during the day. |
| More clothes covering your skin | Sweaters, shawls and other winter clothing leave less skin exposed to sunlight. |
| Smog and haze | Air pollution can reduce the UVB rays that reach your skin. |
Your body stores vitamin D, so the effect of reduced sunlight may not show up immediately. Your levels can fall over several months and may be lowest by late winter or early spring. If you are concerned about a deficiency, your doctor can advise whether you need a blood test.
Vitamin D and Diabetes
People with low vitamin D are more likely to have prediabetes and type 2 diabetes. This does not prove that low vitamin D causes diabetes. Obesity, for example, can lower vitamin D and also raise diabetes risk, because the vitamin is stored in body fat.
Trials give a more cautious picture. In the D2d trial, adults with prediabetes who took 4,000 IU of vitamin D a day did not have a statistically significant reduction in the risk of developing diabetes compared with placebo, although there was a possible small benefit (Pittas et al., 2019). Vitamin D supplements are not a replacement for diet, activity and weight care in diabetes prevention.
Vitamin D and Heart Health
Low levels have also been linked with high blood pressure, heart attack and heart failure in observational studies. But in the large VITAL trial of more than 25,000 adults, vitamin D3 at 2,000 IU a day did not lower the rate of heart attacks, strokes or deaths from cardiovascular disease over about 5 years (Manson et al., 2019).
This means that fixing a low level is important for bones and muscles, but taking extra vitamin D does not protect the heart if your level is already normal. Heart health depends more on blood pressure, cholesterol, blood sugar, weight, activity and smoking.
How to Test for Vitamin D
The usual test is a blood test for 25 hydroxy vitamin D, written as 25(OH)D. Commonly used ranges are:
| Level (ng/mL) | Meaning |
| Below 20 | Deficient |
| 20 to 29 | Insufficient |
| 30 or more | Sufficient |
Laboratories and guidelines differ slightly, so ask your doctor how to read your report. Routine testing is not needed for everyone. It is more useful if you have symptoms, bone disease, kidney or liver disease, poor absorption or high risk.
How to Raise Vitamin D Safely
You can raise your vitamin D levels by getting sensible sun exposure, eating vitamin D-rich foods and taking supplements if your doctor recommends them. Include foods such as oily fish, egg yolks and fortified milk in your diet. If a blood test confirms a deficiency, your doctor can suggest the right supplement dose based on your levels. Avoid taking high-dose vitamin D supplements on your own, as too much can cause health problems.
Sunlight
Sun exposure is the main natural source. Many doctors suggest about 15 to 30 minutes of midday sun on the face, arms and legs, on most days, between roughly 10 am and 3 pm. People with darker skin may need longer. Do not burn your skin and do not use sun exposure as a reason to skip sun protection if you will be outdoors for long. On heavily polluted days, it may be less useful, and when the AQI is poor, staying indoors is wiser.
Food
Few foods have much vitamin D. Useful sources are egg yolk, oily fish such as salmon, sardines and mackerel, fortified milk or oil, and mushrooms exposed to sunlight or UV light. Diet alone rarely corrects a low level.
| “I advise patients to focus on sunlight, a balanced diet and the right supplement dose if their vitamin D levels are low. If your blood test shows a deficiency, do not rely on sunlight or food alone to correct it. Your doctor can help you choose the right dose and decide when to repeat the test.” Dr. Priyadarshini Bhalekar, Zonal Medical Head, Madhavbaug |
Supplements
If your level is low, your doctor may prescribe vitamin D3 in a dose and schedule suited to your level, often weekly or monthly sachets or capsules. The ICMR National Institute of Nutrition recommends 600 IU (15 micrograms) a day for adults to prevent deficiency, and many guidelines set the upper safe limit at 4,000 IU a day without supervision. Too much vitamin D can raise calcium in the blood and cause nausea, vomiting, excess thirst, kidney stones and kidney damage. Do not take high doses on your own or buy long courses without a prescription.
Support for Diabetes and Heart Health at Madhavbaug
Managing diabetes, high blood pressure or heart disease involves more than keeping track of your symptoms. Your diet, daily activity and regular medical check-ups all play a role in your long-term health. At Madhavbaug, doctors assess your condition and medical history before recommending a care plan that may include dietary guidance, exercise advice and suitable Ayurvedic therapies alongside your prescribed treatment.
If you are looking for guided care for a chronic condition, explore our diabetes care programme and heart disease care programme. You can also find a Madhavbaug clinic to discuss your health needs with the medical team.
Looking for guidance on your heart or blood sugar health?
Frequently Asked Questions
What are the early symptoms of vitamin D deficiency?
Tiredness, aching bones or back, muscle weakness and cramps are common. Many people have no symptoms.
What are the signs of low vitamin D in adults?
Bone pain, muscle weakness, frequent fatigue and, in severe cases, softening of bones with a higher risk of fractures.
What is the best time for sunlight for vitamin D in India?
The midday hours, roughly 10 am to 3 pm, give the most UVB. The time needed depends on skin tone, season, location and air quality.
Why does vitamin D fall in winter?
The sun is lower, days are shorter, people wear more clothing and spend less time outdoors and smog blocks UVB.
Does low vitamin D cause diabetes?
Low levels are linked with diabetes but this does not prove cause. Trials of supplements have not clearly shown that they prevent diabetes.
Does vitamin D protect the heart?
A large trial found no reduction in heart attacks or strokes with supplements in the general population. Correcting a deficiency is still important for bone and muscle health.
Can I take vitamin D every day?
Many people take daily doses within the recommended limits, but the right dose depends on your level. Ask your doctor.
Can too much vitamin D be harmful?
Yes. Very high intake can raise calcium levels and harm the kidneys.
References
Sreenivasulu K, et al. Seasonal variation and vitamin D status in ostensibly healthy Indian population: an experience from a tertiary care institute. Metabolism Open. 2024;23:100298.
Pittas AG, et al. Vitamin D supplementation and prevention of type 2 diabetes (D2d). N Engl J Med. 2019;381:520-530.
Manson JE, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). N Engl J Med. 2019;380:33-44.
Holick MF, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96:1911-1930.
Indian Council of Medical Research, National Institute of Nutrition. Nutrient Requirements for Indians: Recommended Dietary Allowances and Estimated Average Requirements. 2020.
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