Vitamin D Deficiency

Medically Reviewed by Poonam Sachdev on April 10, 2024
Written by Stephanie Watson, Lori M. King, PhD
8 min read

A vitamin D deficiency means you don't have enough of this vitamin in your body. You need vitamin D to grow and maintain your bones. You could be at risk for deficiency if you don't get enough sunlight on your skin, you have a disorder that reduces your body's ability to absorb it, or you don't eat enough of it in your diet.

Also known as the sunshine vitamin, your body can make it when your skin is exposed to sunlight. But it's also found in a few foods, such as some fish, fish liver oils, and egg yolks, as well as in fortified dairy products and orange juice.

You need vitamin D to build bones and keep them strong. Vitamin D works to build bones by helping your body absorb and use calcium, magnesium, and phosphate from the food you eat. It balances out the level of calcium in your bones and blood. When you don't take enough vitamin D, your calcium levels drop. Your body has to pull calcium from your bones into your blood to bring your levels back into balance. Vitamin D also plays a role in how your nervous system, immune system, and muscles work.

Vitamin D deficiency can cause weak bones — a condition called osteoporosis in adults and rickets in children. Low blood levels of this vitamin have also been linked to an increased risk for:

  • Cancer
  • Heart disease and stroke
  • Depression
  • Multiple sclerosis
  • Type 2 diabetes

To determine your vitamin D status, your doctor will measure the concentration of 25-hydroxyvitamin D in your blood.

It's challenging to come up with a minimum amount of vitamin D in the blood that will work for most people. Experts agree that it probably varies based on your age, race or ethnicity, and the type of test your doctor orders. However, according to an expert committee of the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine (NASEM):

  • 50 nanograms per milliliter or more is probably too high and may cause health problems
  • 20 nanograms per milliliter or more is probably good enough for most healthy people to maintain overall health
  • 12 nanograms per milliliter or less is considered deficient

Vitamin D deficiency may be categorized in the following way:

  • Mild deficiency: Less than 20 nanograms per milliliter
  • Moderate deficiency: Less than 10 nanograms per milliliter
  • Severe deficiency: Less than 5 nanograms per milliliter

 

Symptoms and signs of vitamin D deficiency tend to be more obvious in kids because they are still growing, so their bone problems are more pronounced. Symptoms of deficiency in kids may include:

  • Weak, sore, and painful muscles (with mild deficiency)
  • Incorrect growth due to bowed or bent bones
  • Muscle weakness
  • Bone pain
  • Joint deformities

Symptoms tend to be less obvious in adults, but they could include:

  • Fatigue
  • Bone and joint pain (especially in your back)
  • Bone loss
  • Muscle weakness, aches, or cramps
  • Mood changes, such as depression

Vitamin D deficiency can happen for several reasons:

You don't get enough vitamin D in your diet. This may be more likely if you follow a strict vegan diet. Most dietary sources are animal-based, including:

  • Fatty fish, especially trout, salmon, tuna, and mackerel
  • Fish liver oils
  • Egg yolks
  • Cheese
  • Some mushrooms
  • Beef liver
  • Fortified foods, such as milk, plant-milk alternatives, and breakfast cereals

You don't get enough sun exposure. Your body makes vitamin D when your face, arms, hands, and legs are exposed to sunlight for about 5-30 minutes a day. You may be at risk of deficiency if you stay inside most of the time, live in a northern climate, or wear sunscreen whenever you go out. Many people are more prone to vitamin D deficiency in winter when there's less sunlight and you spend less time outdoors.

You have dark skin. The pigment that makes human skin dark is called melanin . It helps protect you from ultraviolet B (UVB) light, but it can also block your skin's ability to make vitamin D after sunlight exposure. So, people with darker skin tend to make less vitamin D from sun exposure than those with lighter skin.

You have kidney or liver disease. Vitamin D has an inactive form and an active form that your body can use. Your kidneys and liver have enzymes that convert the inactive form into the active form. Kidney and liver diseases reduce the amount of these enzymes your body makes, which can increase your risk for vitamin D deficiency.

You have a condition that affects your ability to absorb vitamin D. Crohn's disease, cystic fibrosis, and celiac disease make it harder for your intestines to absorb vitamins and nutrients from the food you eat.

You take certain medications. Some medications may make your liver break down vitamin D faster than usual. These medicines include:

  • Carbamazepine, which can be used to control seizures, facial nerve pain, or mania and mixed episodes in people with bipolar I disorder
  • Cholestyramine and colestipol, which are cholesterol-lowering drugs
  • Clotrimazole, which is a medicine used to treat fungal infections
  • Dexamethasone and prednisone, which are steroids used to fight inflammation
  • Nifedipine, which is a medicine used for high blood pressure
  • Orlistat, which is a weight-loss drug
  • Phenobarbital, which can be used to control seizures and relieve anxiety
  • Rifampin, which is an antibiotic used to treat tuberculosis and some cases of meningitis
  • Spironolactone, which is a medicine used for high blood pressure and heart failure

You have obesity.Vitamin D is a fat-soluble vitamin, which means it dissolves in fat. People with a higher level of body fat tend to store more vitamin D in their fat cells. For instance, people with a body mass index (BMI) of 30 or higher are more likely to have low vitamin D in their blood.

You've had weight-loss surgery. Weight-loss surgery that reduces the size of your stomach and/or bypasses part of your small intestines can make it harder for you to absorb nutrients, vitamins, and minerals from your digestive system. Make sure you see your doctor regularly to have your nutrient levels checked.

You may be at higher risk for vitamin D deficiency if you:

  • Are over age 65
  • Have a BMI of 30 or higher
  • Have dark skin
  • Smoke
  • Don't eat or drink vitamin D-fortified foods and drinks

Most people don't need to be screened for vitamin D deficiency, but your doctor may have you take a blood test for it if you have a medical condition or risk factors for vitamin D deficiency or if you have symptoms. The most accurate and most commonly used way to measure how much vitamin D is in your body is the 25-hydroxyvitamin D or 25(OH)D blood test.

In the U.S., the recommended dietary allowance (RDA) of vitamin D is as follows:

  • For infants and babies: 400 international units (IU) a day
  • For children and teens aged 1-18 years: 600 IU a day
  • For adults aged 19-70 years: 600 IU a day
  • For adults aged 70 or older: 800 IU a day

If you have low vitamin D levels, your doctor will likely recommend you take a supplement.

Vitamin D supplements

Vitamin D comes in two forms: ergocalciferol (D2) and cholecalciferol (D3). You need a prescription for D2, but you can buy D3 over the counter. Vitamin D3 seems to be easier for your body to absorb. 

The amount of vitamin D you need to treat your deficiency depends on how deficient you are and your risk factors. Your doctor may start you on a higher dose of 6,000 IU of D3 a day. Once your level goes above 30 nanograms per milliliter, you will usually take a 1,000-2,000 IU supplement per day.

If you are at high risk for vitamin D deficiency because of taking certain medications or having dark skin, obesity, or a condition that keeps you from absorbing nutrients, your doctor may start you on 10,000 IU of D3 a day until your blood level goes above 30 nanograms per milliliter. After that, they may ask you to take 3,000-6,000 IU of vitamin D3 a day.

Children with a vitamin D deficiency will usually get 2,000 IU a day for about 6 weeks until their vitamin D levels in the blood go above 30 nanograms per milliliter. After that, they will take 1,000 IU D3 per day. Nursing infants and children who eat less than 1 liter of vitamin D-fortified milk a day may need to take 400 IU per day of D3.

How long does it take to recover from vitamin D deficiency?

How long it takes you to recover depends on how severe your deficiency is. However, it generally takes about 6-8 weeks of supplementation for your vitamin D levels to go back into the normal range. Even after your Vitamin D levels get normal, your doctor may still have you take supplements for a while to make sure your levels don't fall below normal again.

The way to prevent vitamin D deficiency is to get enough vitamin D in your diet and safe sun exposure.

Diet. Eat foods that have vitamin D. Foods with the most vitamin D (listed from most to least) include:

  • Fatty fish, such as halibut, carp, mackerel, tuna, salmon, sardines, and rainbow trout
  • Cod liver oil
  • Mushrooms
  • Dairy products, especially fortified ones
  • Whole eggs and egg yolks
  • Beef liver
  • Fortified orange juice
  • Fortified cereals

Sun exposure. Stay outside without sunscreen for 5-30 minutes a day. This amount of time will help you make vitamin D without increasing your risk for sunburn and skin cancer.

Supplements. If you don't get enough vitamin D from diet and sun exposure, you may need a supplement. Adults younger than 65 should take 600-800 IU of vitamin D3 each day. Those aged 65 and older need 800-1,000 IU daily.

Vitamin D helps your body use calcium and keeps your bones strong. Having too little of this vitamin increases your risk for weak bones and other health problems. Your doctor can check your vitamin D level with a blood test. If your levels are low, your doctor might suggest you take a daily supplement.

How can I increase my vitamin D levels quickly?

The best way to increase your vitamin D levels is to get some sun on your face, hands, arms, and legs every day for about 5-20 minutes. Also, eat a balanced diet including foods with vitamin D. You can also take supplements, including a multivitamin, which usually includes vitamin D. However, it generally takes at least a week for your vitamin D levels to go up.

What are the warning signs of vitamin D deficiency?

Most people won't notice symptoms of vitamin D deficiency, but if you have any symptoms, go see your doctor. Symptoms may include:

  • Fatigue
  • Bone and joint pain (especially in your back)
  • Bone loss
  • Muscle weakness, aches, or cramps
  • Mood changes, such as depression