Vitamin D gets called the “sunshine vitamin” for a reason. The skin makes it when sunlight hits bare skin, and that simple process helps support strong bones, steady muscles, a balanced mood, and a ready immune system.
Many people, however, spend most of the day indoors, cover their skin, or use strong sunscreen whenever they are outside. Add long winters and desk jobs, and it is easy for vitamin D deficiency to sneak up without clear warning.
Vitamin D deficiency often starts quietly. Symptoms can be mild, vague, or easy to blame on stress or getting older. This guide walks through the top 7 symptoms to watch for, who is most at risk, how testing works, and safe ways to get more vitamin D from sun, food, and supplements. It also reminds readers that only a doctor can confirm the cause of any symptoms.
What Is Vitamin D Deficiency and Why Does It Matter?
Vitamin D deficiency means the level of vitamin D in the blood is lower than the healthy range. In the United States, research up to 2023 suggests that roughly one in four adults has a moderate or severe deficiency, and many more sit in the “low but not quite deficient” zone.
Vitamin D helps the gut absorb calcium from food. Calcium then builds and maintains strong bones and teeth. Vitamin D also supports normal muscle movement, nerve signals, immune defenses, and parts of the brain that affect mood and thinking.
When levels stay low for a long time, bones can become thin and weak. This raises the risk of osteoporosis and fractures. Muscles may lose strength, and infections may show up more often. A detailed overview, like the Cleveland Clinic guide to vitamin D deficiency, explains how wide a role this nutrient plays in everyday health.
Common causes and risk factors include:
- Little or no sun on bare skin
- Living far from the equator or in cloudy regions
- Darker skin, which blocks some UVB rays
- Older age
- Gut diseases that affect absorption, such as celiac or Crohn’s disease
- Liver or kidney disease
- Certain medicines, such as some seizure or HIV drugs
- Obesity, which can trap more vitamin D in fat tissue
- Diets low in vitamin D-rich foods
Paying attention to early signs gives people a chance to act before serious bone or muscle problems appear.
How the Body Gets Vitamin D (Sun, Food, and Supplements)
The body can get vitamin D from three main places:
- Sunlight on bare skin
Ultraviolet B (UVB) rays from the sun hit the skin and trigger vitamin D production. Short, regular exposure is usually the biggest natural source. - Food
Only a few foods contain much vitamin D. Fatty fish, egg yolks, liver, UV-treated mushrooms, and fortified milk or cereal are the main options. - Supplements
Vitamin D tablets, softgels, drops, or gummies can fill gaps when sun and food are not enough.
Modern life often limits sun time. Many people work inside during midday, cover their skin for cultural or personal reasons, or follow strict sun safety rules. Even those living in sunny states can still end up with low levels.
Who Is Most at Risk for Vitamin D Deficiency?
Anyone can develop vitamin D deficiency, but some groups face a higher risk:
- Indoor workers and homebodies
People who rarely go outside during midday get very little UVB exposure. - Those living in northern or very cloudy areas
In many US states, winter sun is too weak for much vitamin D production. - People who cover most of their skin or use high SPF all the time
Clothing and sunscreen block UVB rays, which lowers the vitamin D made in the skin. - People with darker skin
Higher melanin levels act like a natural sunscreen. This protects against burns but slows vitamin D production. - Older adults
Aging skin makes less vitamin D, and kidneys may convert less of it to the active form. - People with gut problems
Conditions like celiac disease, Crohn’s disease, or weight-loss surgery can reduce absorption from food and supplements. - Those with liver or kidney disease
These organs help turn vitamin D into forms the body can use. - People living with obesity
Vitamin D gets stored in body fat, so less is left in the blood.
Anyone in these groups who also notices several symptoms below may want to ask a doctor about a vitamin D blood test.
The Top 7 Symptoms of Vitamin D Deficiency (And What They Feel Like)
Vitamin D deficiency does not look the same for everyone. Some people feel fine. Others notice vague tiredness, weaker muscles, or mood changes that build over time.
Having one symptom never proves vitamin D deficiency. Many health problems share the same signs. Still, a cluster of these symptoms, especially in someone with risk factors, is a good reason to speak with a health professional.
Doctors can check vitamin D levels, review other blood tests, and rule out different causes like thyroid issues, anemia, or sleep disorders.
1. Constant Tiredness and Low Energy
Many people with vitamin D deficiency describe a heavy, dragging tiredness. Sleep might last 8 or 9 hours, but mornings still feel rough. Energy dips hit hard in the afternoon. A person may need extra coffee, naps, or longer breaks just to finish normal tasks.
Vitamin D helps muscles, nerves, and the immune system work smoothly. When levels fall, the body may use energy less efficiently. Fatigue, however, also comes from stress, poor sleep, low iron, or many other conditions, so a doctor visit matters if this feeling does not lift.
2. Achy Bones or Deep Body Pain
Low vitamin D can cause dull, deep pain in bones. The ache often shows up in the lower back, hips, ribs, or legs. It feels different from sharp joint pain or a pulled muscle. Some people describe it as a constant soreness that flares with long walks or standing.
Over time, weak bones can lead to osteoporosis and easier fractures. Anyone with ongoing bone pain, especially older adults, should talk with a doctor. A simple blood test for vitamin D, calcium, and other markers can help uncover what is going on.
3. Muscle Weakness and Trouble Doing Everyday Tasks
Muscle weakness is another common sign. Climbing stairs may feel harder. Standing up from a low couch can take more effort. Carrying grocery bags, picking up a child, or walking long distances may feel shaky or tiring.
Vitamin D helps muscles contract and relax steadily. When levels drop, legs and hips, in particular, can feel unstable. In older adults, this weakness can raise the risk of falls and injuries. Sudden or severe weakness always needs urgent medical care, since strokes, nerve problems, or other illnesses can cause similar problems.
4. Feeling Sad, Blue, or Moody
Vitamin D works in brain areas that affect mood and stress responses. When levels are low, some people notice more sadness, irritability, or stress. Hobbies and social time may feel less fun. Motivation can drop, and small tasks may seem harder.
Studies link low vitamin D with a higher risk of depression, especially in people who get little winter sunlight. Still, mood disorders are complex and involve many factors, such as genetics, life events, and other medical issues. Anyone with strong or lasting sadness, anxiety, or any thoughts of self-harm should reach out to a mental health professional or emergency service right away.
5. Poor Sleep or Restless Nights
Some people with vitamin D deficiency report trouble falling asleep, waking many times at night, or feeling unrefreshed in the morning. Sleep might feel light and restless. Morning headaches or brain fog can follow.
Scientists are still studying how vitamin D affects sleep. It likely plays a role in body clocks, brain chemicals, and muscle relaxation. Simple sleep habits still matter, such as keeping a regular bedtime and limiting screens at night. If sleep stays poor for weeks, and other symptoms like fatigue or muscle pain are also present, a doctor might include vitamin D in a broader blood workup.
6. Hair Thinning or More Shedding Than Usual
Severe vitamin D deficiency can play a role in some types of hair loss. A person may notice more hair in the shower drain, on a brush, or on a pillow. The part line might look wider, or the overall volume may drop.
Hair follicles need nutrients and hormones to stay in the growth phase. Low vitamin D may disrupt that cycle in some people. However, hair loss is also tied to stress, genetics, thyroid disease, pregnancy, certain medicines, and aging. A dermatologist or primary care doctor can help check for multiple causes instead of assuming vitamin D is the only problem.
7. Getting Sick Often or Slow Healing
Vitamin D helps support a healthy immune response. When levels are low, it may be harder for the body to fight germs in the nose, lungs, or skin. Some people notice frequent colds, sinus infections, or chest infections. Cuts, scrapes, or minor surgery wounds may also seem to heal more slowly.
Frequent or serious infections always deserve medical attention. Vitamin D is only one part of immune health, along with sleep, nutrition, stress, vaccines, and other factors. A doctor may decide to test vitamin D while also checking for anemia, diabetes, or other issues that affect healing.
Could It Be Vitamin D Deficiency? When to See a Doctor
Anyone who recognizes several of these symptoms, especially if they last more than a few weeks or affect daily life, should consider talking with a doctor or nurse. This is even more important for people who get little sun, have darker skin, are older, or live with gut or kidney problems.
A health professional can review symptoms, family history, medicines, and lifestyle. They can decide which tests to run and whether vitamin D deficiency is likely or if something else better explains the pattern. Resources like this overview of vitamin D deficiency symptoms and treatment can help prepare questions for that visit, but they never replace medical care.
How Vitamin D Levels Are Tested and What Numbers Mean
The standard test is called 25-hydroxyvitamin D, sometimes written as 25(OH)D. It needs a small blood sample, usually taken from a vein in the arm. Results are reported in nanograms per milliliter (ng/mL).
Different experts set slightly different cutoffs, but many use ranges similar to:
- Very low: under about 10 ng/mL
- Deficient: about 10 to 20 ng/mL
- Insufficient: about 20 to 30 ng/mL
- Sufficient for most people: above about 30 ng/mL
Only a doctor can interpret these numbers in context. For example, someone with osteoporosis, kidney disease, or obesity might need a higher target range or a different treatment plan than a healthy young adult.
Other Conditions That Can Look Like Vitamin D Deficiency
Many problems can cause fatigue, bone or muscle pain, mood changes, and poor sleep. Common examples include:
- Anemia or low iron
- Thyroid disease
- Sleep apnea
- Chronic stress or major depression
- Fibromyalgia or chronic pain disorders
- Nerve problems or spine issues
- Chronic infections or autoimmune disease
Because of this overlap, self-diagnosis is risky. Taking very high doses of vitamin D on a guess can even be harmful. Large daily doses without medical supervision can raise calcium levels too much and damage the kidneys. It is safer to get blood work and follow a tailored plan.
Safe Ways to Boost Vitamin D: Sun, Food, and Smart Supplements
The good news is that vitamin D deficiency is often easy to detect and treat. Most people can improve their levels with a mix of safe sun exposure, smarter food choices, and the right supplement dose, guided by a health professional.
Getting Enough Sun Without Raising Skin Cancer Risk
For many healthy adults, short periods of midday sun on bare skin help raise vitamin D. Experts often suggest about 5 to 30 minutes, two to three times per week, on the face, arms, and legs, depending on skin tone and location. Darker skin usually needs more time than lighter skin for the same effect.
Skin should never burn. People with a history of skin cancer, very fair skin, or many moles should follow their dermatologist’s advice first. In winter or in far northern states, the sun may not provide enough UVB for vitamin D production, so food and supplements play a bigger role.
Everyday Foods That Help Fight Vitamin D Deficiency
Food alone may not fix a strong deficiency, but it supports long-term levels and overall health. Helpful options include:
- Fatty fish such as salmon, mackerel, or sardines
- Cod liver oil
- Egg yolks
- Beef liver in small amounts
- UV-exposed mushrooms
- Fortified cow’s milk and many plant milks
- Fortified breakfast cereals
- Some brands of fortified orange juice
Simple habits can help, such as grilled salmon once a week, scrambled eggs for breakfast, or a bowl of fortified cereal with milk. Reading labels for “vitamin D fortified” makes it easier to spot good options at the store.
When Supplements Make Sense and How Much to Take
Supplements are often the most reliable way to correct Vitamin D Deficiency, especially in people who cannot get much sun or have absorption problems. Vitamin D3 (cholecalciferol) is usually preferred over D2 because it tends to keep blood levels higher for longer.
General guideline ranges often suggest about 600 IU per day for most people aged 1 to 70 and about 800 IU per day for adults over 70. Some doctors use higher short-term doses to correct a strong deficiency, then switch to a lower maintenance dose.
Most adults are advised not to exceed 4,000 IU per day on a long-term basis without medical supervision, due to the risk of vitamin D toxicity. People who are pregnant, take many medicines, or have kidney or liver disease should always ask a doctor before adding or changing supplements.
Conclusion
Vitamin D deficiency is common, but it does not need to stay hidden. Fatigue, bone pain, muscle weakness, mood changes, poor sleep, extra hair shedding, and frequent infections can all be part of the picture, especially in people who get little sun or have other risk factors.
Having one or two of these signs does not prove low vitamin D, yet it is a signal to pay attention. A simple blood test and a short talk with a health professional can bring clear answers and a safe plan.
By aiming for a healthy mix of safe sun, vitamin D-rich foods, and smart supplements when needed, anyone can protect their bones, muscles, mood, and immune system over the long term. The next step is simple: take note of any symptoms, think honestly about sun habits and diet, and discuss vitamin D testing with a trusted doctor if there is any concern.
