Best Time to Take Vitamin D: With Food, D2 vs D3 and the Upper Limit

The best time to take vitamin D is with a meal that contains some fat. Vitamin D is fat-soluble, meaning it dissolves in fat rather than water. In a 2015 study, the peak level of vitamin D in the blood after a single dose was about 32 percent higher when it was taken with a breakfast containing fat than with a fat-free one, and the kind of fat did not matter. Some vitamin D is absorbed even without fat, so a dose taken on its own is not wasted. Pairing it with a meal is simply an easy improvement.

The hour you take it matters much less. The absorption studies changed the meal, not the time of day. What keeps your blood level steady is taking it consistently, so choose the meal you rarely skip. Beyond timing, two choices matter more: vitamin D3 generally raises blood levels more than D2, and adults should stay at or below 4,000 IU (100 mcg) a day unless a clinician prescribes more.

Quick guide

Here are six questions and their short answers.

Question	Short answer
With or without food?	With a meal that contains some fat
Morning or night?	Either; pick the meal you eat most reliably
D2 or D3?	D3 usually raises blood levels more
How much do adults need?	600 IU (15 mcg) a day up to age 70; 800 IU (20 mcg) after 70
Upper limit for ages 9 and older	4,000 IU (100 mcg) a day
Routine blood test?	Not recommended for healthy adults without symptoms

Why fat helps

The NIH Office of Dietary Supplements (ODS) explains that both forms of vitamin D are well absorbed in the small intestine. Having fat in the gut at the same time improves absorption, although some vitamin D gets through even without dietary fat.

The clearest test of this is a 2015 study of 50 healthy older adults, published in the Journal of the Academy of Nutrition and Dietetics. After an overnight fast, each person took a single 50,000 IU dose of vitamin D3 with a test breakfast. The breakfast was either fat-free or had 30 percent of its calories from fat. The peak level of vitamin D3 in the blood, measured 12 hours later, was about 32 percent higher in the groups whose breakfast contained fat. Whether that fat was mainly monounsaturated or polyunsaturated made no significant difference.

The study has two limits worth knowing. First, it looked at one large test dose over about 14 hours, not months of daily use. That dose was a research tool, not a routine amount to take. Second, it measured vitamin D itself rather than 25-hydroxyvitamin D, the longer-lasting form doctors test. Still, it supports the simple habit of taking vitamin D with food.

Because absorption depends on the gut’s ability to absorb fat in general, some people absorb less. ODS notes that people with conditions that make fat harder to absorb, such as some forms of liver disease, cystic fibrosis, celiac disease, Crohn’s disease and ulcerative colitis, are at higher risk of low vitamin D. So are people who have had gastric bypass surgery.

Morning or night?

We found no good evidence that taking vitamin D in the morning rather than the evening changes how well it is absorbed. The research has compared meals, not hours. So pick the time that fits your day:

• If your biggest meal with some fat is dinner, take it then.
• If breakfast is your most reliable meal and includes eggs, yogurt, milk, nut butter or avocado, take it then.
• If you take a once-weekly or larger prescribed dose, follow your clinician’s schedule and still pair it with food.

D2 vs D3

Supplements contain one of two forms: vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol). ODS says they differ only in a small part of their structure, both are well absorbed, and both raise blood levels of 25-hydroxyvitamin D. Most evidence, though, shows that D3 raises those levels more and keeps them higher for longer.

A 2012 meta-analysis of randomized trials, published in the American Journal of Clinical Nutrition, pooled studies comparing the two and found D3 more effective overall. The gap was strongest with large single or infrequent doses and was not clear with daily dosing. So for a modest daily amount, either form will work. If you are choosing, D3 has the edge.

On labels, 1 mcg of vitamin D equals 40 IU.

How much you need, and the upper limit

These amounts come from the ODS fact sheet. For babies, the figures are Adequate Intakes. The upper limit is the most you should take in a day from all sources combined.

Age	Recommended daily amount	Upper limit
0 to 6 months	400 IU (10 mcg)	1,000 IU (25 mcg)
7 to 12 months	400 IU (10 mcg)	1,500 IU (38 mcg)
1 to 3 years	600 IU (15 mcg)	2,500 IU (63 mcg)
4 to 8 years	600 IU (15 mcg)	3,000 IU (75 mcg)
9 to 70 years, including pregnancy and breastfeeding	600 IU (15 mcg)	4,000 IU (100 mcg)
Over 70 years	800 IU (20 mcg)	4,000 IU (100 mcg)

To see your own values next to other vitamins and minerals, use our nutrient RDA lookup.

More is not better. ODS notes that the Food and Nutrition Board advised avoiding blood levels above about 50 to 60 ng/mL, and that even intakes below the upper limit might cause problems over time.

Too much vitamin D raises the amount of calcium in your blood. ODS lists nausea, vomiting, muscle weakness, changes in mood or thinking such as confusion, pain, loss of appetite, dehydration, passing a lot of urine, strong thirst and kidney stones. In extreme cases it can lead to kidney failure and heart rhythm problems. Toxicity almost always comes from supplements, including manufacturing errors and wrong doses, not from sunlight.

Sun, food and supplements

MedlinePlus, the U.S. National Library of Medicine’s health information service, describes three sources of vitamin D:

• Sunlight: your skin makes it when bare skin, without sunscreen, is in sunlight outdoors.
• Food: a few foods contain it naturally, such as egg yolks, liver and fatty fish, and it is added to many others, including breakfast cereals, milk and other dairy foods.
• Supplements: these come as pills or liquid drops.

ODS notes that the recommended amounts assume minimal sun exposure, because sun varies so much with season, location, skin and habits. That is why a supplement can make sense for people who spend most daylight hours indoors, cover up outside or live where winter sun is weak, even if they eat well.

Fortified foods count toward your total. If you drink fortified milk and eat fortified cereal, add them in so that food and supplements together stay under the upper limit.

Do you need a blood test?

For most healthy adults, no. The U.S. Preventive Services Task Force concluded that the evidence is not strong enough to weigh the benefits and harms of screening adults without symptoms for low vitamin D. ODS adds that the Endocrine Society does not recommend routine testing in healthy people.

MedlinePlus explains when testing is used. A clinician may order it when they suspect a bone or other condition is linked to low vitamin D. It is also used when risk is high, for example if you rarely get sun on bare skin, have a condition that affects how you absorb nutrients, have kidney or liver disease, or take medicines that affect vitamin D.

The test measures 25-hydroxyvitamin D. ODS gives the usual thresholds:

• Below 12 ng/mL (30 nmol/L): risk of deficiency.
• 20 ng/mL (50 nmol/L) or more: enough for most people.
• Above 50 ng/mL (125 nmol/L): may be linked to harmful effects.

Medicines and other supplements

ODS lists several interactions worth raising with your pharmacist before you start:

• Orlistat: this weight-loss medicine can reduce how much vitamin D you absorb.
• Statins: they may reduce vitamin D production, and high vitamin D intakes might make some statins work less well.
• Corticosteroids: medicines such as prednisone can interfere with how your body processes vitamin D.
• Thiazide diuretics: these water pills combined with vitamin D supplements might push blood calcium too high, especially in older adults.
• Calcium supplements: taking them with vitamin D may raise the risk of certain side effects.

If you take magnesium too, a shared mealtime makes an easy routine; our guide to the best time to take magnesium covers the medicine gaps that apply to it.

Who should be careful

• Kidney and calcium problems: if you have kidney disease, hyperparathyroidism, or a history of high blood calcium or kidney stones, take vitamin D only as your clinician directs.
• Certain medicines: if you take thiazide diuretics, statins, corticosteroids or orlistat, ask your pharmacist before starting.
• High or stacked doses: take care if you take more than 4,000 IU a day, or combine several products that contain vitamin D, such as a multivitamin plus a separate supplement.
• Children: upper limits are much lower in early childhood, so check the age row in the table above before choosing a product.
• Pregnancy and breastfeeding: the recommended amount is 600 IU a day, but confirm any supplement plan with your clinician.