Recommended doses should be individualized based on dietary and sun exposure habits and the latitude of the country, and they can also be adjusted according to body mass index, age, and skin color, with obese, elderly, and dark-skinned people needing higher doses.
A vitamin D deficiency can occur when usual intake is lower than recommended levels over time, exposure to sunlight is limited, the kidneys cannot convert 25(OH)D to its active form, or absorption of vitamin D from the digestive tract is inadequate.  Fish liver oil and fatty fish are the best sources of foods with D vitamin.  Vitamin D-deficient diets are associated with milk allergy, lactose intolerance, ovo-vegetarianism, and veganism. Other groups at risk for D vitamin deficiency include:

  • breastfed infants
  • infants of mothers who have D vitamin deficiency
  • the elderly (due to reduced capacity to absorb D vitamin)
  • people who do not get outside regularly
  • dark skinned people
  • people covering their bodies
  • people with Crohns disease, liver disease, cystic fibrosis, kidney disease
  • children and adults who are obese or have had gastric bypass surgery
  • people with fat malabsorption problems
  • people taking medications: anticonvulsants,  glucocorticoids, antifungals or cholesterol reducing medications

The infants D vitamin status is dependent on the mothers D vitamin status at birth. The pregnant mother with vitamin D deficiency will have an infant that is deficient in D vitamin.  Low infant levels are associated with increased risk for RS virus, as well as developing asthma and diabetes 1 later in life. Besides supplementing the infant, the breastfeeding mother is recommended to take a dose of 4000 IU so the infant gets adequate levels.

Children with a low vitamin D present with a higher incidence of fractures from normal activities, they are at risk for diabetes type 1.

Recommended Dietary Allowances (RDAs) for Vitamin D and tolerable upper intake levels are all far below the dosages considered to be harmful. The tables below show these doses. These are doses recommended for healthy people. Taking the lower limit is sufficient during the summer (fall and spring depends on latitude) for healthy individuals not in a risk group. The upper intake levels are appropriate for risk groups. Individuals who have already a deficiency, require in some cases even higher levels to correct, treat och prevent D vitamin deficiency and should be monitored by a physician.

The following table shows the range of vitamin D which can be safely taken based on age. The list shows different alternatives for strength depending on how the manufacturer measures the D vitamin. Vitamins should be taken from september through April, and earlier if the summer is rainy and cloudy.

What can be confusing is how different articles discuss different measurements of D vitamin: IU is the international unit while μgm (mcg) is microgram. (400 IU = 10 μgm  = 10 mcg).

0 -6 months the daily dosage should be between 400-1000 IU or 10-25 μgm (mcg)

7 months to 1 year: 400-1500 IU (IE) or 10-38 μgm (mcg)

1-3 years 600-2500 IU (IE) or 15-63 μgm (mcg)

4-8 years 600-3000 IU (IE) or 15-75 μgm (mcg)

9-18 years 600-4000 IU (IE) or 15- 100  μgm (mcg)

adults 2500-4000 IU (IE) or 63 – 100 μgm (mcg)

women who are pregnant or lactating 600-4000 IU or 15-100 μgm (mcg).

An important study published in 2017 provides research to support increased daily recommendations for D vitamin in all age groups.

When is D-vitamin too much or too little?
Experts in Endocrinology express the following opinion ” vitamin D deficiency is very common in all age groups — essentially everyone is at risk”.  Our main source of D vitamin is through sunlight exposure directly to the skin during the summer. Vitamin D is otherwise available in only a few foods and as a supplement. In northern latitudes, particularly Scandinavia, there is a risk for not meeting your daily requirements depending on the weather. From September through April D vitamin needs to be supplemented due to the northern latitude and lack of exposure to the sun.  Vitamin D is most well know for its role with calcium for skeletal health, building strong bones! Vitamin D has other important functions including enhancing and supporting the immune system, regulating cell growth and proliferation, reducing inflammation and neuromuscular health. There are a wealth of studies focusing on the link between D vitamin deficiency and cancer, depression, cardiovascular disease, MS, infections, inflammatory diseases and diabetes.

The best way to measure D vitamin in the body is under discussion, but experts agree that a serum 25(OH)D levels <75 nmol/L may be too low for safety and associated with higher all-cause mortality.  There is a call to all health care professionals to promote intake levels corresponding to those proposed by the Endocrine Society Expert Committee (2011) as safe upper tolerable daily intake doses for patients at risk for vitamin D deficiency (<50 nmol/L): 2000 IU for those <1 year of age, 4000 IU for those aged 1-18 years, and 10 000 IU for those aged >18 years (Papadimitriou, 2017).

Can patients get too much vitamin D?
Too much vitamin D can be toxic, but is very rare. Studies investigating toxicity all involved daily consumption of over 40000 IU (1000 mcg) per day. Immediate symptoms of toxicity are abdominal cramps, nausea and vomiting. Symptoms can otherwise be due to an underlying magnesium deficiency. Vitamin D toxicity can be determined by a blood test. The first sign is hypercalcemia, a high level of calcium in the urine.  There are some health conditions which affect how the body metabolizes vitamin D and calcium, particularly hyperparathyroidism or kidney disease. People with these health conditions should be under supervision when taking D vitamin supplements.

Överdosering.

Tillskott med D-vitamin har länge hämmats av en rädsla för överdosering. Denna rädsla har nu visat sig vara kraftigt överdriven. Omvandlingen till den aktiva formen sker i flera steg vilket är en inbyggd säkerhetsmekanism. I studier har dosbehov och säkerhet undersökts. Dessa talar för att 100 mikrogram (=4.000 IE) vitamin D3/dag ger tillfredsställande nivåer utan biverkningsrisk. Jämför detta med livsmedelsverkets rekommendation på 400 IE per dag som alltså bara utgör 10% av optimal dos. Referens: www.lakartidningen.se/engine.php?articleId=6