How Much Vitamin D Do I Need?

If you have paid the least bit of attention to health care coverage in the past few years, you probably have noticed the growing number of studies citing that insufficient levels of vitamin D contribute to elevated disease risk from myriad illnesses ranging from autoimmune disorders, cardiovascular disease, and osteoporosis all the way to cancer and diabetes. So you might be wondering, how much vitamin D do I need each day?

The answer to this question is a bit complicated because there are significant variations in vitamin D needs for some people. First I’ll give a rule of thumb that works reasonably well for most people. Later I’ll add some additional considerations that may significantly affect appropriate dosage.

Basic Guidelines for Vitamin D3

A simple rule of thumb you can use to determine how much vitamin D you should consume each day is based upon the observation that 100 IU of vitamin D3 will raise the blood level of an adult by about 1 ng/mL. Vitamin D researchers are widely recommending blood levels of between 40 to 60 ng/mL (conservative) or 50 to 80 ng/mL (newer recommendation with growing acceptance). For a typical adult getting little vitamin D from food or sun (the common case), supplementing with vitamin D3 at 4000 IU to 8000 IU per day is appropriate depending upon your target for your vitamin D blood test.

In the past couple of years as vitamin D3 dosages recommendations have been raised, 5000 IU vitamin D3 softgels have become very inexpensive. Most such products use tiny softgels that are easy to swallow even for senior citizens. Another reason I like the 5000 IU softgels is that their vitamin D3 is already dissolved in an oily fat. Compared to powders, powder capsules, and tablets, this makes it more likely the active ingredients will be absorbed in the digestive tract.

For adults, 5000 IU per day is a good “rule of thumb” starting point for vitamin D3 supplementation. This 5000 IU per day also applies to teenagers who are roughly adult-sized, typically those around 14 years of age or older.

For teenagers and adults, a suitable inexpensive product that has tiny softgels of 5000 IU each is Swanson Health Care Products High Potency Vitamin D-3 5000 IU that features 250 softgels for $8.99. That’s about as inexpensive as vitamin D3 supplements can be unless you find a good sale. So for around $1 per month with that product, most adults can get enough vitamin D3 via supplementation. A good alternative is NOW Foods Vitamin D3 5000 IU 240 softgels, but this usually runs about $14 per bottle.

Preschool kids need about 1000 IU of vitamin D3 per day. As they are often unable or unwilling to swallow softgels, you may find it easiest to add this to their food via vitamin D3 drops. Customer reviews of Carlson Labs Carlson For Kids Liquid Vitamin D3 Drops, 400 IU, 365 drops 10ml suggest this is a good product for kids because it has no taste and can mix unobtrusively and easily with any drink or food containing some fat. You could easily put a drop of this in the food or drink for each meal to get about 1200 IU of vitamin D3 per day. Some report using these drops successfully directly in the mouth of their kids, also.

School age kids prior to growing to near the size of adults would benefit from around 2000 IU to 3000 IU of vitamin D3 per day, either drops or the usually cheaper softgels if you can get the kids to swallow them. For kids who can’t handle tiny softgels, you might try Carlson Labs D Drops Liquid Vitamin D3 4000 IU every other day or four drops per weeks as they are 4000 IU per drop and are also tasteless.

If your kids will swallow softgels, the high potency 5000 IU softgel products I mentioned should be fine for them simply by taking them less often than every day. For example, for a school age kid prior to teenagers in high school, swallowing three or four of the 5000 IU softgels per week is about right to get around 2000 IU to 3000 IU per day on average. Unless water soluble vitamins (most forms of B and C vitamins in particular), this works because vitamin D3 is fat soluble and the body stores it for future use.

If you have trouble getting your kids or yourself to take vitamin D3 supplements every day, it is fine to take all of them for the week at once with a big meal containing fat for best absorption. Even if you sometimes accidentally give two big doses per week because you forgot when the last dose was, it is unlikely to create any health problem unless you do this often.

Safe Upper Limits for Vitamin D3

According to Dr. John Cannell of the Vitamin D Council, overdose from taking a massive quantity of vitamin D3 during one day is less likely than overdose from water, aspirin, or Tylenol. To further drive this home, there is no known successful suicide attempt using vitamin D. The estimated LD50 (lethal dose for 50% of the patients taking it) for vitamin D3 in humans would be approximately 168 bottles containing 250 capsules of 1000 IU each or about 33 bottles containing 250 softgels of 5000 IU each. Can you imagine taking even one bottle of vitamin D capsules or softgels in one day? If you’re still not convinced that vitamin D is not likely to kill anybody in one or two attempts even if they tried very hard to do themselves in with it, see How Much Vitamin D is Too Much? Take This Vitamin D Quiz to Find Out!.

The main risks for vitamin D are not acute overdose but instead chronic overconsumption risks that show up not via death but by initially mild symptoms that can easily be reversed simply by lowering an overly high vitamin D intake. According to Dr. Michael Holick, the generally safe upper limits for long-term daily vitamin D3 intake for healthy weight people are 10,000 IU per day for adults (and similar size teens), 5000 IU per day for preschool and school age kids, and 2000 IU per day for kids under 1 year old.

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Quoted from an interview with Michael F. Holick, PhD, MD The Pioneer of Vitamin D Research:

LE: What are the misperceptions about vitamin D supplementation in terms of toxicity?

MH: I talk about this a lot when I give talks to physicians. I joke about this by saying to them that the one thing doctors remember from medical school more than anything else is…don’t ever make your patient vitamin D intoxicated. However, they’ve never seen vitamin D intoxication and they don’t even know what it is. Yet, despite all of the new information about vitamin D, they still believe that taking 50,000 IU of vitamin D once a week for eight weeks to treat vitamin D deficiency is going to cause vitamin D intoxication. We did a study with Dr. Heaney in 2002 and showed that you can take up to 10,000 IU of vitamin D a day for almost a half a year and not worry about vitamin D intoxication. In The Vitamin D Solution, I suggest that for children during the first year of life, up to 2,000 IU of vitamin D a day is safe. Children from age 1 to 12 years 5,000 IU of vitamin D a day is safe. All teenagers and adults can easily tolerate 10,000 IU of vitamin D a day without concern for toxicity.

So far it appears that as long as you don’t drive your vitamin D levels up beyond 100 ng/mL, there is little risk from the supplement and much to gain. The primary risk that has been identified involving high vitamin D levels short of severe chronic overdoses (such as taking over 50,000 IU per day for extended periods) is atrial fibrillation. This was noticed in a study of 132,000 patients run by the American Heart Association.

Quoted from New Study Warns Against Excessive Vitamin D Intake:

As the population ages, an increasing percentage develops an irregular rhythm in the upper chambers of the heart called atrial fibrillation. It is the most common type of heart arrhythmia and approximately 5% of persons over 65 years of age are expected to be diagnosed with it.5

In patients with low, low-normal, normal, and high-normal levels of vitamin D, there was no increased risk of atrial fibrillation. Those with excess levels (above 100 ng/mL) of vitamin D had 2.5 times greater risk of atrial fibrillation compared to those with lower levels.

The authors of this study recommended that people have their blood tested to ensure they are taking the proper dose of vitamin D.

We at Life Extension long ago noted wide dose-response variability with vitamin D and recommended 25-hydroxyvitamin D blood tests to ensure our members are in the optimal range of between 50–80 ng/mL.

Most members are surprised that even taking 5,000 IU a day (or more) of supplemental vitamin D does not always get them above 50 ng/mL. In rare instances, however, doses of less than 5,000 IU result in blood levels greater than 100 ng/mL.

These real world findings confirm the importance of checking one’s vitamin D blood status after initiating a daily dose significantly higher than 2,000 IU to establish how much vitamin D is individually needed to achieve optimal ranges (50–80 ng/mL) and not excess levels (over 100 ng/mL).

Levels of vitamin D above 100 ng/mL are not a common risk. Less than one quarter of 1% of the 132,000 patients in the study had vitamin D levels that high or higher. Also, there is debate that the real culprit behind the observed increased atrial fibrillation may be low thyroid function. So don’t let this 100 ng/mL upper limit for vitamin D blood tests scare you away from vitamin D supplementation. The same study showed significantly lower rates of many diseases for those with vitamin D levels in the normal (41 to 80 ng/mL) and high normal (81 ng/mL to 100 ng/mL) levels versus those with inadequate vitamin D at 40 ng/mL or lower.

Sunlight Exposure

Younger people who spent a lot of time in the sun around noon tend to need less vitamin D supplementation. Their skin when exposed to the midday sun produces significant quantities of vitamin D. The skin’s vitamin D production capability declines with age, fortunately the ability to absorb vitamin D from diet and supplements does not. So if you’re in your 30s or younger and spend a lot of time outside without sunscreen or head-to-toe clothing between the hours of 10 AM to 3 PM, you might be getting a significant amount of vitamin D from the skin’s reaction to sunlight. (Early morning and late afternoon sun is not sufficiently bright to cause much vitamin D production in the skin even if most of your body is fully exposed without sunscreen.) For everybody else, however, the amount of sun-generated vitamin D is probably not significant.

As a rule of thumb, cut your vitamin D3 intake from the general guideline by 50% if you spend an hour or more in the midday sun everyday without much clothing or sunscreen. Few people other than lifeguards and possibly some construction, landscaping, and farming workers are likely to fall into that group. Consequently, most people shouldn’t bother figuring sun exposure into their vitamin D3 intake because it is likely to be sporadic, unpredictable, and contribute little overall to vitamin D status.

Skin Color

An additional factor to consider is the color of your skin. If you have light skin, sunlight will cause more vitamin D generation in the skin. Darker skin features more pigmentation that blocks UV light that triggers vitamin D synthesis, just as sunscreen and clothing do. People who have dark skin should consider bumping up their vitamin D3 supplementation a bit to cover from the lower incidental amounts they will get from common levels of sun exposure. As a rough guideline, adding another 10% to 20% to your daily dosage. For instance if you’re from Tamil Nadu or Africa and are taking 5000 IU per day, you might add a second 5000 IU softgel once per week to compensate for your darker skin.

Body Weight and Obesity

Vitamin D is fat soluble. People with higher levels of body fat therefore tend to sequester much of their vitamin D in fat cells where it is not available to improve the body’s biochemical functions. If you have little body fat, you may need less vitamin D. If you are significantly overweight or obese, you may need even two or three times as much vitamin D as somebody of a similar height with a more healthy weight and fat level.

To make this adjustment, use a Body Mass Index calculator to compute your BMI. If you are overweight (BMI 25 to 29.9) then increase your suggested vitamin D dosage by 50%. If you are obese (BMI 30 and above), then double it.

It is particularly important for the overweight and obese to get vitamin D blood tests. That’s because even taking 10,000 IU per day for years may be inadequate to attain optimal vitamin D levels in these people. For example, a 5 foot 6 person weighing 200 pounds or more could easily require more than 20,000 IU per day and it simply is not safe to be supplementing at those levels for years without periodic blood tests because there is an increased risk of atrial fibrillation when vitamin D blood levels exceed 100 ng/mL. This almost never happens with 5000 IU dosages even after years, but the overweight and obese simply cannot depend upon 5000 IU being enough to get their vitamin D levels up into the 40 ng/mL to 80 ng/mL range as it would do in most healthy weight people.

Because vitamin D3 response is so connected to weight or more precisely fat levels, if your weight changes significantly (say more than 10%) then you should consider getting another vitamin D3 blood test sometime in the next several months. It is important to verify that your daily intake is still getting the results you want. This is doubly important if you were obese or far overweight and have lost much weight as this loss of fat can boost your vitamin D response and you want to avoid going over the 100 ng/mL level that is viewed as the starting point for elevated risk of atrial fibrillation caused by calcium deposits inside the heart.

Vitamin A Intake

If you take a lot of preformed vitamin A per day, such as you may find in cod liver oil and many multivitamins, you also may need more vitamin D3. If that’s the case, consider replacing some of your preformed vitamin A intake with beta carotene that can be converted by most people’s bodies to vitamin A as necessary. Here’s a relevant bit of information that illustrates the point:

Quoted from Excess Vitamin A Can Thwart Vitamin D:

Preformed vitamin A is active retinol as opposed to beta-carotene that can convert to retinol in the body. We reviewed 14 popular multivitamin formulas and found the average amount of preformed vitamin A to be 4,395 IU, while the average vitamin D content was only 407 IU.

The problem with this potency ratio is that in the presence of excess preformed vitamin A, the beneficial effects of vitamin D can be neutralized.73

The first hint of this problem occurred when a group of doctors reviewed historical medical records on the use of cod liver oil to prevent respiratory infections. In the 1930s, two large controlled studies showed that cod liver oil reduced incidence of common colds by 50% and respiratory infections by 30% in adults.74-77

A study published in year 2004 showed that cod liver oil and a multivitamin slightly reduced mean number of respiratory infections in children, but the total number of doctor visits for these infections was slightly higher in the cod liver oil/multivitamin group (68 versus 61).78 The 1930s study demonstrated far superior benefits with cod liver oil.74-77

One difference between these studies is that cod liver oil in the 1930s study had more vitamin D. The other issue is that children in the 2004 study received 3,500 IU of preformed vitamin A (not beta-carotene) and only 700 IU of vitamin D.

Given what we now know, a more appropriate dose should have been 500-1,000 IU of vitamin A (instead of 3,500 IU used in the 2004 study) and 2,000-3,000 IU of vitamin D3 (as opposed to 700 IU used in the 2004 study).

The quote above is from Life Extension, a great resource for helpful information, quality supplements, and inexpensive vitamin D blood tests if your regular doctor or insurance is mired in obsolete medical science and refuses to order a routine vitamin D blood test at your request.

Chronic Illness

People who are suffering from chronic illnesses such as cancer, asthma, incurable viral infections, diabetes, and other conditions may need even more vitamin D than those who are not. There’s no simple estimate for the need for additional vitamin D for such people, but they are far more likely to be severely deficient than the general person on the street who does not have a chronic illness. What these ill people can do to get started on their supplementation more quickly is to take 100,000 IU of vitamin D3 per day for a week or so at the start to load up on vitamin D quickly. Then they can drop down to the daily dosage they picked which again should be for most people 5000 IU or higher per day for adults. After at least two or three months of taking this amount daily, then get a vitamin D blood test to check the results and then adjust up or down accordingly.

Infectious Illness Such as Flu

Health care advocate Dr. Joseph Mercola produced the following video about flu vaccines and infections that advocates people who think they have caught the flu should take a large dose of vitamin D right away and repeat this each day for the first three days of feeling sick. He thinks this is much better and safer practice than getting a flu shot each year. The section mentioning vitamin D starts about 4 minutes and 30 seconds into the video.

Mercola’s opinion is that the daily dose of vitamin D for kids is about 2000 IU per day and for adults between 5000 IU and 10,000 IU per day.

If you get the flu, Mercola says you can often prevent the worst of it by taking a lot of vitamin D right away. He suggests taking 2000 IU per kilogram of body weight once per day for three days. (For Americans reading this, to get your weight in kilograms simply divide your weight in pounds by 2.2 since there are 2.2 pounds per kilogram.) Then multiply your weight in kilograms by 2000 IU. Take this dose once per day for three days when you feel you are getting sick with the flu. So for example, if you weight 150 pounds, your daily “sick dose” for three days is 150 / 2.2 * 2000 IU = 136,364 IU. To make it simple, round it to the nearest 5000 IU and then take the necessary number of 5000 IU vitamin D softgels to get that dose. So in our example, you’d need 135,000 IU / 5000 IU per softgel = 27 softgels. That’s a lot, so you might divide it to 9 per meal.

Adjusting Your Vitamin D3 Dosage Over Time

I’d suggest for starters you shoot for 50 ng/mL initially which for teens and adults matches well with the inexpensive 5000 IU softgels. After you have supplemented for half a year, get a vitamin D blood test and then raise your target to 60 ng/mL and adjust your daily dosage according to your test result.

As an example, say you have been taking 5000 IU per day and get a test result of 47 ng/mL after half a year of supplementing. Simply divide your new target of 60 by 47 and multiply by 5000 IU (your current dosage) to get your new daily dosage of 6383 IU per day. Since that’s not an easy number to exactly match, keep taking your daily 5000 IU and then once per week take another two 5000 IU softgels. That works out to 45,000 IU per week or 6249 IU per day which is plenty close enough. Retest after a year and repeat the adjustment. After a couple of years, you should find that your dosage becomes reasonably stable and you may not need to test any more often then every few years.

For more detailed information on adjusting your vitamin D dosage including how to adjust for vitamin D2 (rather than D3) found in some supplements, please see a previous article Adjusting Your Vitamin D Intake to Optimal Levels.

May Be Able to Drop Calcium Supplements

If you are taking calcium supplements, you may find that once you elevate your vitamin D level, you may not need the calcium supplements any longer. That’s because vitamin D is very effective at raising calcium absorption from food. The savings from the calcium supplements would likely pay for the vitamin D3 supplements.

Vitamin D3 Works Best With Vitamin K2 and Magnesium

Prevention of osteoporosis and cardiovascular diseases are two of the main benefits of optimizing your vitamin D levels. However, vitamin D alone is not enough to get the best possible benefits. You also need vitamin K, and in particular vitamin K2. While vitamin K1 is important for blood clotting processes, it is the K2 form that helps produce MGP (matrix Gla-protein) to keep calcium in the bones where it belongs and prevents calcification of the arteries and heart. The human body isn’t very good at converting K1 to K2, so you need to get it from diet or supplements. I highly recommend that you look into significant supplementation with 1 mg (1000 mcg) or more per day of vitamin K2 to help ensure that the calcium your body absorbs better via higher vitamin D levels doesn’t end up causing arterial calcification, atrial fibrillation, or other cardiovascular disease. The benefits of K2 to bone and cardiovascular health are well established. More recently, there is also growing evidence that vitamin K2 may also be very important to brain health and likely also has a role in slowing the development of insulin resistant conditions such as metabolic syndrome and diabetes.

If you are using “blood thinners” such as warfarin or Coumadin, please realize they are dangerous for long-term use largely because they severely interfere with vitamin K activity. This can be overcome to some degree by adding more vitamin K to your diet, but then the anticoagulation effect can be lessened leaving you more susceptible to dangerous blood clots. Vitamin K supplementation for warfarin users realistically requires adjustments to your diet and supplements to help lower your overall clotting risk in other ways along with careful adjustments of medication based upon blood clotting test results. Warfarin patients must consult with their doctors about vitamin K supplementation. Alternative anticoagulants that are not dependent upon blocking vitamin K activity may be preferable for some of these patients. Others may be able to get some vitamin K benefits by adjusting the warfarin dosage plus consistent use of a vitamin K supplement.

Magnesium is also important to bone health. In recent years, studies have been showing a large portion of the population is deficient in magnesium. The increasing use of bottled and purified water is believed to be contributing to lower magnesium intake. Therefore you should also look into supplementing with 400 mg or more of magnesium each day in addition to vitamins D3 and K2.

Further Reading

Vitamin D May Help Fight Asthma And Flu

Low Vitamin D Common in African-American Asthma Kids

70% of US Children Have Low Vitamin D Levels

Michael F. Holick, PhD, MD The Pioneer of Vitamin D Research

Vitamin D’s Crucial Role in Cardiovascular Protection

Vitamin D: Cancer Prevention and Other New Uses

New Study Warns Against Excessive Vitamin D Intake

Flawed Calcium and Heart Attack Study Misleads Consumers

Vitamin D, Vitamin A and Cancer

Vitamin K: Protection Against Arterial Calcification, Bone Loss, Cancer, and Aging!

Latest Study on Vitamin K and Coronary Heart Disease

Vitamin D deficiency: a worldwide problem with health consequences

Vitamin D Deficiency: This clandestine endemic disease is veiled no more

Risk assessment for vitamin D

Matrix Gla-protein: the calcification inhibitor in need of vitamin K

Is Your Bottled Water Killing You?

Magnesium: Widespread Deficiency with Deadly Consequences

These statements have not been evaluated by the Food and Drug Administration. The products mentioned in this post and on this website are not intended to diagnose, treat, cure or prevent any disease. The information presented here is for educational purposes and does not constitute medical advice. Please obtain medical advice from qualified healthcare providers. Pursuant to FTC regulations, please be aware some of the links herein may be affiliate iinks. If you click on them and complete a purchase, this website may earn a commission.

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