The Most Effective Vitamin D3 Dosage, According to a Nutrition Coach

Step outside on a sunny day, and you can soak up some free vitamin D — the sunshine vitamin. Vitamin D is vital to healthy bones and your immune system. Getting enough vitamin D through sun exposure and food sources alone is difficult. Over one billion people worldwide have a vitamin D deficiency, which can lead to medical conditions. (1)

I always recommend that my clients get their vitamin D levels checked to see if their healthcare provider suggests a vitamin D supplement. There are two forms of vitamin D: vitamin D2 and vitamin D3. Here, I’ll zero in on vitamin D3, potentially the most effective option for raising your vitamin D levels. I’ll explain what it is, how much you need, and how it may affect your health.

What Is Vitamin D3?

Vitamin D is a fat-soluble vitamin (along with vitamins A, E, and K), which is stored in fat in your body. Vitamin D refers to a group of vitamins that includes vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). How much vitamin D2 and D3 you have determines your vitamin D status — insufficiency, adequate levels, or toxicity (very rare). (2)(3)

You can get vitamin D3 from food sources like fortified cereals, dairy products, egg yolks, fatty fish, and sardines. You can also take vitamin D supplements, multivitamins that contain vitamin D3, or cod liver oil. (3)

Your body also synthesizes and produces vitamin D3 in your skin from ultraviolet rays during sun exposure. Wearing sunscreen may limit how much vitamin D you can get from sun exposure. However, too much exposure to ultraviolet rays without sunscreen is a leading risk factor for skin cancer, so it’s not the safest way to get your daily vitamin D. (4)

What Does Vitamin D3 Do?

Vitamin D’s primary function is to balance your body’s calcium and phosphorus levels by helping you absorb calcium. These functions are important for bone health, muscle and nerve function, your immune system, and cardiovascular health. (2)(5)

Vitamin D3 (cholecalciferol) may be the most effective dietary supplement for raising your blood levels of vitamin D. It is recommended by health professionals for people with a vitamin D deficiency. Certain populations may be more at risk of having low vitamin D levels, including older adults, people with darker skin, people who spend less time in the sun, and people with gastrointestinal diseases. (6)(7)

[Read More: The Benefits of Vitamin D for Strength Athletes]

Vitamin D3 (along with calcium supplements) is often used to treat three bone health conditions that a vitamin D deficiency can cause. (7)

• Rickets (soft and weak bones in children)
• Osteomalacia (soft and weak bones in adults)
• Osteoporosis (thin and weakening bones in older adults)

How Much Vitamin D Do You Need?

A vitamin D deficiency is extremely common. Over one billion people worldwide, across all countries, ages, and ethnicities, have low vitamin D. (1)

[Read More: The Vitamins and Nutrients You Need To Take To Stay Fit Over 40]

The Office of Dietary Supplements Department of the National Institutes of Health (NIH) recommends the following daily vitamin D intake for Americans: (8)

• Infants from birth to one year need 0 micrograms (mcg) or 400 international units (IU) of vitamin D.
• People from one to 70 years 15 mcg or 600 IU of vitamin D daily. Pregnant and breastfeeding people require the same amount.
• Older adults over age 71 need 20 mcg or 800 IU of vitamin D.

How Do You Know If You’re Getting Enough Vitamin D?

Concerned about your vitamin D status? A healthcare provider can check it with a blood test. The test will show your blood levels of 25-hydroxyvitamin D. 

The amount of 25-hydroxyvitamin D indicates your overall vitamin D blood levels. Having more than 30 ng/mL of 25-hydroxyvitamin D is adequate. (9)

[Read More: What Vitamins Should Women Take On a Daily Basis?]

Here are some more numbers to look for. (5)

• Insufficiency: 30 nmol/L (12 ng/mL) is too low and can harm your bone health
• Sufficiency: 50 nmol/L (20 ng/mL) is adequate for bone health
• Toxicity: Over 125 nmol/L (50 ng/mL) is too high

Do Vitamin D Supplements Work?

Research shows that vitamin D supplements do work at raising your blood levels of vitamin D. It is difficult to get enough vitamin D from food sources since they contain low levels of it. It can also be dangerous for your skin to try and get enough from the sun alone. (7)

[Read More: What Men Should Look For in a Multivitamin]

Always check with a healthcare provider for personal medical advice.

Can You Have Too Much Vitamin D?

Vitamin D toxicity is rare but possible. It can occur from taking high doses of vitamin D and going above the recommendation. A blood test indicating vitamin D toxicity would show your 25-hydroxyvitamin D level higher than 150 ng/ml (375 nmol/l). (10)

Symptoms of a vitamin D overdose include loss of appetite, nausea, vomiting, constipation, and muscle weakness. An overdose and vitamin D toxicity can cause hypercalcemia, a condition where your calcium blood levels are too high. Hypercalcemia can lead to nausea, vomiting, muscle weakness, kidney stones, pain, and dehydration. (7)(8)

[Read More: The 7 Best Multivitamins for Women]

The NIH states the daily upper limit for vitamin D is 100 mcg (4,000 IU) for people over nine. (8)

Uses of Vitamin D3

Research links a vitamin D deficiency with multiple medical conditions related to bone health, cardiovascular diseases, autoimmune diseases, type 2 diabetes, cancer, and depression. However, outcomes from clinical trials have been mixed across the board. (9)

Effective for Raising Vitamin D Levels

One thing seems to be relatively sure — taking vitamin D3 as a dietary supplement effectively raises blood levels of vitamin D.

• A meta-analysis of clinical trials from 1966 to 2011 found that vitamin D3 is more effective at raising 25-hydroxyvitamin D levels than vitamin D2. (6)
• A study on 32 older adults with a vitamin D deficiency found that vitamin D3 was almost twice as effective as vitamin D2 at raising 25-hydroxyvitamin D levels. (11)

Probably Effective for Bone Health and Immune System Strength

Raising vitamin D levels by taking vitamin D3 seems to be effective at improving bone health. 

• Long-term vitamin D or calcium insufficiency may cause osteoporosis. Since vitamin D helps absorb calcium, both can help with prevention. Clinical trials on older adults of all genders suggest that both vitamin D and calcium supplementation can increase bone mineral density. (8)
• Having adequate vitamin D levels is associated with higher bone mineral density, which helps prevent osteoporosis. Older adults, especially people assigned female at birth, are more at risk of developing osteoporosis, which can increase their risk of fractures. (12)

It is well known that vitamin D plays a significant role in regulating your immune system. (13)

• Research has found that immune cells contain vitamin D receptors. Theoretically, exposing them to vitamin D supplements could help to “strengthen” your immune system. There seems to be a link between vitamin D deficiency and autoimmune diseases. (13)
• When your immune cells receive vitamin D, it may help protect you from infections. Vitamin D may increase your immune response. (14) 
• A study on college athletes found that lower vitamin D levels in the winter were associated with a higher risk of illness. (15)

Possibly Effective for Blood Pressure and Cholesterol Levels

Some clinical trials suggest vitamin D supplements may help reduce high cholesterol and blood pressure. Both are risk factors for heart disease. (5)

[Read More: Combating the Winter Blues this Winter? Start With Vitamin D]

However, health professionals state that vitamin D supplements alone are not an adequate treatment for cholesterol and blood pressure levels.

Seems Ineffective for Weight Loss and Preventing Certain Conditions

Although vitamin D deficiency seems to correlate with certain medical conditions, clinical trials show that vitamin D supplements don’t necessarily help them — other than those related to bone health. They also seem ineffective in helping with weight loss.

• Weight Loss: Although people with obesity frequently have low vitamin D levels, clinical trials do not show that vitamin D helps with weight loss. If you are trying to lose weight and have a vitamin D deficiency, taking vitamin D may benefit your health — but it won’t impact weight loss. (8)
• Cardiovascular Disease: High vitamin D levels have been associated with a lower risk of cardiovascular disease, but it doesn’t go the other way. Clinical trials show vitamin D supplements do not help prevent heart disease. (5)(8)
• Multiple Sclerosis: Some studies found a link between low vitamin D levels and a higher risk of developing multiple sclerosis (MS). However, clinical trials haven’t shown that vitamin D supplements can help prevent or manage MS. (5)(8)
• Depression, Cancer, and Type 2 Diabetes: Research states that vitamin D supplements do not help prevent or manage depression, cancer, or type 2 diabetes. (5)

Side Effects of Vitamin D3

Vitamin D3 dietary supplements may cause side effects. Always consult a healthcare provider before trying a new supplement, and let them know if you experience worsening side effects.

Here are the common side effects of vitamin D supplements: (7)

• Lack of appetite
• Unexplained weight loss
• Nausea
• Constipation
• Vomiting

Vitamin D3 Interactions 

Vitamin D3 may interact with certain medications by causing your body to absorb too little or too much vitamin D and calcium. Here’s what to look out for. (5)

• Weight Loss Drugs: The drug Orlistat can prevent your body from absorbing vitamin D from food and dietary supplements.
• Cholesterol Drugs: Taking vitamin D supplements may reduce the efficacy of cholesterol-lowering drugs (a class called statins), including atorvastatin, lovastatin, and simvastatin.
• Steroids: Taking a steroid medication like prednisone may lower vitamin D levels. 
• Diuretics: Taking diuretic medications (Hygroton, Lozol, and Microzide) with vitamin D supplements can increase your calcium levels too much.

It’s also important to tell your healthcare provider if you already take calcium supplements, multivitamins, and other vitamin D supplements or eat fortified foods. Taking vitamin D3 in addition to these could raise your vitamin D or calcium levels too much. (5)

Since vitamin D is a fat-soluble vitamin, taking vitamin D supplements with a fat source may help improve absorption. One meta-analysis of trials found that omega-3 supplements helps increase vitamin D levels. (16)

There isn’t any concrete evidence that omega-3 can help improve vitamin D absorption, but if you take both supplements separately, it may be worth trying them together. 

Takeaways

Here’s what you need to take with you.

• Vitamin D: a fat-soluble vitamin critical for bone health and calcium absorption
• Vitamin D Deficiency: over one billion people worldwide don’t get enough
• Vitamin D2 and Vitamin D3 influence your vitamin D levels
• How to Check Your Levels: ask your healthcare provider for a blood test

• Deficiency, Sufficiency, Toxicity: your doctor will let you know, but here are the numbers for vitamin D blood levels
  • Insufficiency: 30 nmol/L (12 ng/mL) and under
  • Sufficiency: 50 nmol/L (20 ng/mL) and over
  • Toxicity: Over 125 nmol/L (50 ng/mL) and over
• Why Take Vitamin D3: it raises vitamin D levels best
  • it’s challenging to get it all through food
  • it’s dangerous to get it all through sun exposure without sunscreen
  • it contributes to healthy bones
  • helps prevent rickets, osteomalacia, and osteoporosis
  • may boost the immune system to prevent infections
• How Much to Take: 
  • RDA for adults: 15 mcg or 600 IU 
  • RDA for adults over age 71: 20 mcg or 800 IU
  • Upper Limit: don’t go over 4,000 IU daily
• Side Effects: watch out for
  • decreased appetite
  • unexplained weight loss
  • nausea, vomiting, constipation
• Interactions: vitamin D3 may interact with
  • weight loss drugs, cholesterol drugs, steroids, and diuretics
  • calcium supplements and multivitamins

Frequently Asked Questions

Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.

References

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3. Alayed Albarri EM, Sameer Alnuaimi A, Abdelghani D. Effectiveness of vitamin D2 compared with vitamin D3 replacement therapy in a primary healthcare setting: a retrospective cohort study. Qatar Med J. 2022 Aug 4;2022(3):29. 
4. D’Orazio J, Jarrett S, Amaro-Ortiz A, Scott T. UV radiation and the skin. Int J Mol Sci. 2013 Jun 7;14(6):12222-48.
5. U.S. Department of Health and Human Services. Vitamin D Fact Sheet for Consumers. National Institutes of Health.
6. Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, Chope G, Hyppönen E, Berry J, Vieth R, Lanham-New S. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012 Jun;95(6):1357-64.
7. National Library of Medicine (2020, October 15). Cholecalciferol (Vitamin D3). Medline Plus.
8. U.S. Department of Health and Human Services. Vitamin D Fact Sheet for Health Professionals. National Institutes of Health.
9. Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. 
10. Marcinowska-Suchowierska E, Kupisz-Urbańska M, Łukaszkiewicz J, Płudowski P, Jones G. Vitamin D Toxicity-A Clinical Perspective. Front Endocrinol (Lausanne). 2018 Sep 20;9:550. 
11. Romagnoli E, Mascia ML, Cipriani C, Fassino V, Mazzei F, D’Erasmo E, Carnevale V, Scillitani A, Minisola S. Short and long-term variations in serum calciotropic hormones after a single very large dose of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) in the elderly. J Clin Endocrinol Metab. 2008 Aug;93(8):3015-20. 
12. Laird E, Ward M, McSorley E, Strain JJ, Wallace J. Vitamin D and bone health: potential mechanisms. Nutrients. 2010 Jul;2(7):693-724. 
13. Martens PJ, Gysemans C, Verstuyf A, Mathieu AC. Vitamin D’s Effect on Immune Function. Nutrients. 2020 Apr 28;12(5):1248. 
14. Aranow C. Vitamin D and the immune system. J Investig Med. 2011 Aug;59(6):881-6. 
15. Halliday TM, Peterson NJ, Thomas JJ, Kleppinger K, Hollis BW, Larson-Meyer DE. Vitamin D status relative to diet, lifestyle, injury, and illness in college athletes. Med Sci Sports Exerc. 2011 Feb;43(2):335-43. 
16. Alhabeeb H, Kord-Varkaneh H, Tan SC, Găman MA, Otayf BY, Qadri AA, Alomar O, Salem H, Al-Badawi IA, Abu-Zaid A. The influence of omega-3 supplementation on vitamin D levels in humans: a systematic review and dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2022;62(11):3116-3123.

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