vitamin d low symptoms, vitamin d defiiency symptoms, vitamin d deficiency symptoms adults

Vitamin D Low Symptoms & Red Flags

Last modified on October 19th, 2023

We’re hearing more and more about the importance of vitamin D and making sure you aren’t experiencing vitamin D low symptoms. Below, we go into what the symptoms of a vitamin D insufficiency are, why it’s such an essential vitamin, and also how you can raise your levels quickly.

Since we are approaching cold and flu season, understanding the so-called sunshine vitamin and how much you need is even more critical.

Most Common Vitamin D Low Symptoms

The following are more commonly seen in patients with vitamin D deficiency symptoms.

Getting Sick Frequently

Vitamin D is critical for your immune system to function correctly. Without enough, your immune system won’t be able to adequately fight back against bacteria and viruses, according to the U.S. Food and Drug Administration. 

The vitamin interacts directly with your cells that fight infections.

If you notice you’re someone who gets sick often or easily, you should consider having your vitamin D levels checked.

Research shows taking a daily dosage of up to 4000 IU  may reduce your risk of developing respiratory tract infections.

Autoimmune Disease

Research is continuing to come out about the role of vitamin D in autoimmune diseases.

For example, in one study published recently, low vitamin D levels were found to impact B-cell hyperactivity, interferon-a, and autoantibody production in patients with systemic lupus erythematosus.

Low vitamin D levels or lower-than-recommended dietary allowance can play a role in other autoimmune conditions including hypothyroidism, Hashimoto’s, and multiple sclerosis.

Also associated with low levels of fat-soluble vitamins are inflammatory bowel disease and rheumatoid arthritis.

Vitamin D can promote regulatory T cells. Those T cells dictate whether to promote or dampen inflammation. Around 90% of people with an autoimmune disorder have a genetic defect that promotes deficiency of vitamin D.

Excessive Sweating

The potential to experience excessive seating is one of the lesser-known symptoms of vitamin D deficiency. It can be one of the first symptoms that people have.

When you sweat for no apparent reason, or you seem to be sweating more than what’s in proportion to what you’re doing, it may indicate you need to get higher amounts of vitamin D. 

Sweating around the head, in particular, could be a sign of D deficiency.

Depressive Symptoms and Affective Disorders

Vitamin D deficiency may have a link to depression and mood disorders. For example, in 2013, a meta-analysis found study participants with depression had co-occurring low vitamin D levels. In the same review, people with low D levels were at a much higher risk of depression statistically.

Getting enough vitamin D is vital for your brain function, and the receptors for this vitamin are in the same parts of your brain associated with depression.

Symptoms of depression can include feeling sad, hopeless, or helpless, insomnia, excessive sleepiness, and loss of interest in things you enjoyed at one point. Weight loss or gain, lethargy, concentration problems, and memory issues can also occur when you’re experiencing depression.

Along with depression stemming from having low levels of the fat-soluble vitamin, reduced levels are linked with other psychiatric disorders.

In some research, supplementing with vitamin D helps with anxiety symptoms.

There are also associations with seasonal affective disorder (SAD). Seasonal affective disorder is a type of depression associated with seasonal change. If you have symptoms of SAD, they’ll usually begin and end at the same time each year. Your symptoms will start in the fall and then get better as spring approaches.

You may feel low-energy, moody, and generally low. Along with vitamin D, light therapy, medications, and talk therapy may help symptoms of SAD.

In general, proper nutrition is essential for cognitive health. Insufficient vitamin intake can significantly increase your risk of a range of cognitive impairment and mental health disorders. 


One of the primary symptoms of vitamin D deficiency that many people experience is fatigue or sluggishness.

If you’re exhausted during the day or at abnormal times, there’s the potential that it’s because of deficiency.

Hair Loss

If your hair is falling out more than usual or you’re suffering from alopecia, there’s evidence it could be due to low vitamin D levels. In particular, female pattern hair loss tends to associate with D.

Your skin metabolizes the vitamin. These are skin cells that process keratin. Keratin is a protein in your skin, hair, and nails. If you don’t have enough D, keratinocytes in your hair follicles have a hard time regulating hair growth and shedding.

Over time, being deficient in this vitamin could worsen your hair loss. Among young people with hair loss, one study found women had a more significant D deficiency.

Supplementing with D can help you combat your hair loss if this is the reason for it, or you can get 10 to 30 minutes of sun.

Thin, Brittle Nails

One symptom of deficiency that you can see outwardly is peeling or thin nails.

Your nails, like your hair, are made from keratin. When you don’t have vitamin D, it leads to imbalances in your calcium and phosphorous levels. D helps your body absorb calcium. If you don’t have adequate vitamin D, calcium is excreted instead of absorbed.

Then you can notice the peeling or thin nails.

Migraine Headaches

A few studies show a relationship between your D levels and headaches, including migraine. There is a relationship between not only levels of the vitamin but also migraine severity. Some researchers find that supplementing with a dose between 1000 and 4000 IU/d could reduce migraine frequency.

Slow Wound Healing

If you have wounds that appear to take a long time to heal, there may be a connection between vitamin D and this symptom. The vitamin helps regulate compounds like growth factors that your body uses to form new tissue.

In one study, people with leg ulcers were more likely to have deficiencies of the vitamin. Researchers found after study participants took 50,000 international units of vitamin D every week for two months, they had improvements in wound healing.

Stress Fracture Risk and Broken Bones

If you’re prone to bone fractures that don’t heal quickly, check your vitamin levels. D helps your body absorb calcium. Calcium is critical to bone health. When you have adequate levels of the vitamin it helps promote bone health and prevent osteoporosis.

If you’re deficient, you may be at high risk of fractures because of reduced calcium absorption. You need the vitamin for healthy bones, according to the Office of Dietary Supplements. 

With inadequate vitamin levels, your bone density and bone mass can be in jeopardy. You may be at higher risk of osteoporotic fractures. 

Muscle Pain and Weakness 

Low levels of D can cause increased muscle and joint pain. Physical deficiency symptoms can worsen rheumatoid arthritis pain, affecting the knees, legs, and hips.

Researchers think one reason low vitamin levels are linked to weakness and pain is because of its anti-inflammatory effects.

If you suffer from chronic pain, you should also think about whether or not it’s linked to a deficiency of this key vitamin.

There’s something called osteomalacia which perhaps has associations with D deficiency. Osteomalacia includes dull, aching pain. The pain can get worse at night or when you’re putting weight on the bones affected. This could even explain morning back pain.

Vitamin deficiency may not be the only reason for chronic pain, but it’s looking more like it could be a common contributor.

Weight Gain

Obesity is a risk factor for this vitamin deficiency. Research also shows if you’re deficient it can increase your risk of gaining weight. These effects are particularly prominent in men but occur in women too.

In one study including men and women, low levels of the vitamin seemed to be associated with increased overall weight and abdominal fat.

Dizziness and Vertigo

Sometimes when people have vitamin D low symptoms, they can include dizziness and vertigo. Researchers found in patients with vertigo, vitamin D supplementation significantly helped their symptoms when combined with calcium tablets.

Specifically, researchers think D deficiency is linked to a common type of vertigo—benign paroxysmal positional vertigo or BPPV.

Children with Vitamin D Deficiency

When children are deficient in this critical vitamin, which is more common than parents may think, it can cause brittle bones and frequent fractures.

In children, deficiency can contribute to suppressed immunity and rickets, as well as muscle weakness and delayed development.

A child with a deficiency might experience bone pain, especially in the lower limb long bone. The pain could keep them up at night.

What is Vitamin D?

Vitamin D is fat-soluble.

  • The vitamin plays an important role in skeletal function and integrity, immune system regulation, and electrolyte reabsorption.
  • The vitamin is also called calciferol.
  • There are a few foods with naturally occurring vitamin D.
  • Your skin can also produce vitamin D when ultraviolet rays hit it.
  • The vitamin helps promote calcium absorption in the gut and helps with normalizing bone mineralization.
  • Having adequate vitamin D can reduce inflammation.
  • Adequate vitamin levels can also modulate immune function and cell growth, and cell differentiation and proliferation.

Complications of Vitamin D Deficiency

Some potential severe health issues can occur if you have untreated vitamin D deficiency. These complications include:

  • Rickets: This condition is rare in the U.S. and affects babies and pre-school-age children. Sometimes older children are affected too. Rickets in children affects joints, wrists, bones, and knees.
  • Cardiovascular disease: There is a link between your levels of vitamin D and the risk of heart-related diseases. These connections likely stem from the fact vitamin D combats inflammation, protecting your heart and helping stabilize blood pressure. You could be at greater risk of hypertension and metabolic syndrome if you’re deficient in the vitamin.
  • Autoimmune disease: Vitamin D naturally modulates the immune system. Low levels may link to the development of autoimmune disorders, including Crohn’s disease, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis.
  • Low blood calcium: This condition is called hypocalcemia.
  • Osteomalacia in adults: This condition causes soft bones in adults. You need this vitamin for strong bones, especially as you age. It’s something for postmenopausal women to pay attention to in particular, as well as the risk of osteoporosis in adults. 

Causes of Vitamin D Low Symptoms

The causes of vitamin D deficiency symptoms can occur due to certain risk factors. The risk of vitamin D deficiency can stem from:

  • Having darker skin: When you have more pigment melanin in your skin, it reduces your ability to produce vitamin D from the sun. For example, black Americans usually have lower serum vitamin D levels than white Americans because of dark skin.
  • Being older: When you’re older you’re at particular risk of developing a lack of vitamin D. Your skin’s ability to synthesize the vitamin goes down as you age. Also, older people tend to spend more time indoors than younger people.
  • Being overweight or obese: People with a body mass index (BMI) of 30 or more have lower serum D levels than nonobese people. While being obese doesn’t affect your skin’s ability to synthesize the vitamin, if you have more subcutaneous fat, it could hold onto the vitamin. If you’re obese, you may need more vitamin D to achieve the same blood levels as someone who’s not obese.
  • Not having a lot of dairy, beef liver, or fish in your diet, which are natural sources of vitamin D
  • Living somewhere far from the equator where you don’t get a lot of sun year-round
  • Always wearing sunscreen when you go outside. It’s important to protect yourself from skin cancer, but you do still need some sun exposure to ensure you’re getting the beneficial effects of vitamin D. 
  • Having disorders like chronic kidney disease or liver disease: These disorders can cause problems with the absorption of vitamins. When you get older, your kidneys are less able to convert vitamin D to the active form, increasing the risk of deficiency.
  • Spending most of your time indoors
  • Health conditions that affect your absorption of vitamin D like Crohn’s or celiac disease: Vitamin D is fat-soluble. The absorption depends on the ability of your gut to absorb fat. Fat malabsorption is associated with a number of conditions.
  • Having gastric bypass surgery: When you have bariatric surgery, part of your small intestine is bypassed. That’s’ where the vitamin is absorbed. The vitamin that makes its way into your bloodstream from fat stores may not raise your levels adequately, leading to vitamin D inadequacy. 
  • Using medications that can affect your vitamin D metabolism  and serum concentrations, like steroids and statins

What To Do If You Notice Vitamin D Low Symptoms

If you notice what you think are signs of vitamin D deficiency, you should speak to your doctor or a health care professional. They can check your vitamin D status.

It’s important you have your levels checked rather than assuming you have a deficiency.

You don’t want to take too much of the vitamin, plus another health disorder could cause your symptoms.

If you’re vitamin D deficient the signs can be very subtle and take time to recognize.

Since so many people are actually deficient and the symptoms are difficult to notice at least at first, you should ask your doctor to check your D levels regularly.

A simple blood test can do screening for vitamin D levels.

The test is the 25-hydroxyvitamin D blood test. Talk to your healthcare provider if you have concerns about sufficient vitamin status. 

What Should Your Vitamin D Level Be?

Your vitamin D level should be at least 20 nanograms/milliliters to 50 ng/mL. Anything less than 12 ng/mL is considered a severe vitamin deficiency. 

With that being said, even if you have at least 20 ng/mL, you might still need to find ways to get more vitamin D. Many medical professionals consider levels between 20 and 29 ng/mL to be suboptimal, even if those levels don’t technically show deficiency.

If you’re deficient in the vitamin, you should follow the guide below for supplementation.


Daily Dose

Weekly Dose

Maintenance Dose

Infants/Toddlers (0-1 years old)

2,000 IU for 6 weeks

50,000 IU for 6 weeks

400-1,000 IU/day

Children (1-18 years old)

2,000 IU for 6 weeks

50,000 IU for 6 weeks

600-1,000 IU/day


6,000 IU for 8 weeks

50,000 IU for 8 weeks

1,500-2,000 IU/day

Obese people/people with malabsorption/individuals taking certain medications

6,000-10,000 IU


3,000-6,000 IU/day

The U.S. National Academy of Medicine suggests a daily intake of up to 4,000 IU of vitamin D a day is a safe treatment for vitamin D deficiency for most people.

Higher doses are temporarily needed to raise blood levels in some people. Those doses are what’s listed above.

How to Raise Your Vitamin D Levels Quickly

The prevalence of vitamin D deficiency is estimated at around 13% worldwide. It’s a significant health concern. Above, we list a chart to follow for supplementing. There are other things you can do to raise your levels as well.

  • Get exposure to sunlight. Your skin has a type of cholesterol that functions as a D precursor. When the compound in your skin is exposed to UV-B radiation from the sun, it becomes D. When you get sun exposure, the vitamin you create may circulate for twice as long as getting it from food or supplements.
  • Eat fatty, oily fish and other types of seafood. Seafood high in the vitamin includes tuna, oysters, and mackerel. Salmon is high in D, as are sardines and anchovies. Some fish oil may have a high content of the vitamin too. You can also take cod liver oil. 
  • Have mushrooms, which are the only vegetarian foods rich in the vitamin. Mushrooms make their own D with exposure to UV light like humans.
  • Make sure you’re eating the egg yolk to get your daily requirement. Pasture-raised or free-range chickens tend to have eggs with much higher levels of vitamin D content. 
  • Certain food sources are fortified with the vitamin, including cow’s milk, orange juice, and cereal. Fortified foods can also include tofu. 
  • UV-B lamps can be a way to raise D levels, but they can be expensive. You can only use them for around 15 minutes at a time to avoid burns if you aren’t able to get direct sunlight exposure naturally. 

What to Know About Vitamin D Dietary Supplements

If you’re experiencing vitamin D low symptoms, one way to improve them may be with a daily supplement. 

There are two types of this fat-soluble vitamin. Fat-soluble vitamins dissolve in fats and oils. Your body can store them for long periods.

There are two primary dietary common forms of the vitamin. 

Vitamin D3 is cholecalciferol. This form of vitamin D is in animal foods like egg yolks and fatty fish.

Vitamin D2 supplements are ergocalciferol which is in mushrooms and some plants.

Cholecalciferol or vitamin D3 seems to be as much as twice as effective at raising your level of vitamin D compared to D2 versions, according to the National Institutes of Health. 

When you’re using supplements as a way to get nutrients and health benefits, you have to keep in mind that they don’t work in isolation. They often work with one another. If you increase your intake of one vitamin or nutrient, you may need more of another.

Fat-soluble vitamins tend to work together, so you should pay attention to your intake of vitamins A and K when you’re taking D3. K2 is especially important because it’s a fat-soluble vitamin many of us are deficient in. You should also ensure you’re getting enough magnesium because it is vital for the function of D.

Vitamin D toxicity is rare but can happen if you take more than 60,000 IU of the vitamin regularly. It usually takes months of an extreme dose for toxicity in healthy people well beyond the upper limit of a recommended dose. 

How to Choose a Supplement

Tips for choosing a high-quality vitamin D supplement include:

  • The recommended common form is vitamin D3 or cholecalciferol. This is the type your body makes from the sun. Vitamin D2 is not the type your body naturally produces, which is why D3 is recommended as a supplement.
  • Look for USP-verified supplements, which indicate potency.
  • Be aware that vitamin D3 supplements are from animal sources. If you’re vegan, you’ll have to choose vitamin D2 even though D3 is more bioavailable. Even so, D2 can still be effective in helping you maintain blood levels of the vitamin.
  • Sublingual vitamin supplements have more availability in your body, so you can put them to use. When you take a tablet supplement, they’re broken down in your gastrointestinal tract. Then, how well they’re ultimately absorbed varies depending on your digestive health, intestinal floral, and digestive enzymes. When you use a sublingual form, meaning it goes under your tongue, it bypasses your digestive system. The mucous membranes of your mouth absorb the vitamin. There is a network of capillaries that then deliver the vitamin directly to your bloodstream. In one study, the sublingual use of vitamin D led to absorption three to 10 times higher than other forms of the supplement.
  • Consider finding a supplemental vitamin with magnesium or take the two together. Magnesium helps activate vitamin D, and the enzymes that metabolize the vitamin need magnesium.
  • Since D is a fat-soluble vitamin, it’s a good idea to take it when you’re having a meal with a healthy fat like eggs, olive oil, nuts, or avocado.
  • Be careful about taking a D supplement before bed. The vitamin can work oppositely as melatonin, a sleep hormone. If you take vitamin D supplements at night your melatonin levels are naturally high, which could interfere with your sleep quality.
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symptoms of a vitamin deficiency

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Vitamin D Low Symptoms—Final Thoughts

In some ways, vitamin D deficiency is a significant health crisis. Immune function, cancer, autoimmune disease and heart health are all affected by vitamin D levels as some other medical conditions. We see that cancer mortality rates tend to be lower in people when they have a sufficient serum 25-hydroxyvitamin D level based on clinical trial evidence. 

If you suspect you’re experiencing vitamin D deficiency symptoms, it’s important to talk to your health care provider and consider options to raise your levels.

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