Quick answer

At recommended amounts, vitamin D rarely causes side effects. Trouble comes from taking too much for months, which drives blood calcium up. The adult upper limit is 100 mcg (4,000 IU) a day from all sources, and in a five-year trial, 2,000 IU a day caused no more problems than a placebo.^1,2,3

Key facts

Too much vitamin D almost always comes from supplements, not from food or sunshine.¹
Signs of too much are unlikely below 250 mcg (10,000 IU) a day, but NIH notes that even intakes under the upper limit might cause harm over time.²
Blood levels above 50 ng/mL (125 nmol/L) are linked to possible harm.^1,2
About 3 in 100 US adults take 4,000 IU or more of vitamin D a day.²

At normal amounts

Side effects are uncommon at 2,000 IU a day. In VITAL, that amount taken for about five years caused no more high blood calcium, kidney stones or stomach complaints than placebo.³

That trial gave 2,000 IU a day, more than three times the 600 IU most adults need, to about half of its 25,871 adults for a median of 5.3 years. The recommended 600 to 800 IU sits far below the amounts linked to harm.^1,2,3

Signs of too much

Too much vitamin D raises blood calcium. Signs include nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, passing a lot of urine, great thirst and kidney stones. They are linked to blood levels far above normal, usually over 150 ng/mL (375 nmol/L).^1,2

Extremely high levels can cause kidney failure, calcium deposits in soft tissues, an irregular heartbeat and even death. Such cases almost always come from far too much vitamin D in supplements, including products made with manufacturing errors, taken wrongly or prescribed in error.^1,2

If you take a high-dose supplement and notice these signs, stop it and call your doctor. A blood test can check your calcium and vitamin D levels.¹

Where the limits are

The upper limit for adults and children aged 9 and over is 100 mcg (4,000 IU) a day from all sources, including during pregnancy and breastfeeding. It is 25 mcg (1,000 IU) for babies up to 6 months, 38 mcg (1,500 IU) from 7 to 12 months, 63 mcg (2,500 IU) at ages 1 to 3 and 75 mcg (3,000 IU) at ages 4 to 8. Signs of toxicity are unlikely below 250 mcg (10,000 IU) a day, but NIH notes that even intakes below the upper limit might cause harm over time.^1,2

Where common amounts sit^1,2,3
Amount	Where it sits
15 to 20 mcg (600 to 800 IU) a day	Recommended for adults
50 mcg (2,000 IU) a day	Half the adult upper limit; given for five years in VITAL
100 mcg (4,000 IU) a day	Adult upper limit, all sources combined
250 mcg (10,000 IU) a day	Below this, signs of toxicity are unlikely
Blood level over 150 ng/mL	Typical of vitamin D toxicity

Sun on the skin cannot cause vitamin D toxicity, because the skin limits how much it makes. Frequent use of tanning beds, however, can push blood levels very high.^1,2

Calcium, kidney stones and other cautions

Taking calcium with vitamin D can raise the chance of kidney stones. In the Women's Health Initiative, 36,282 women after menopause given 1,000 mg of calcium and 400 IU of vitamin D a day had 17% more kidney stones over 7 years than those on placebo.²

NIH notes that Black Americans might have a greater risk than White Americans of falls and fractures with daily intakes of 50 mcg (2,000 IU) or more.²

Medicines that interact with vitamin D

Ask your pharmacist or doctor first

Thiazide diuretics, water pills such as hydrochlorothiazide, chlorthalidone and indapamide, reduce the calcium lost in urine. Together with vitamin D supplements, which raise calcium absorption, they might push blood calcium too high, especially in older adults and people with reduced kidney function or an overactive parathyroid gland. This applies to thiazides, not to every kind of water pill.^1,2

Expected from how the two work, not shown in studies

Ask your pharmacist or doctor first

High intakes of vitamin D, especially from supplements, might make atorvastatin, lovastatin and simvastatin less potent, because they appear to compete for the same enzyme that breaks them down. Statins may also reduce the body's own production of vitamin D.^1,2

Reported in studies

Your doctor may want to check on you

Corticosteroid tablets such as prednisone can reduce calcium absorption and interfere with how the body uses vitamin D. In a US survey, very low vitamin D levels were twice as common among people taking oral steroids (11%) as among those who were not (5%).^1,2

Reported in studies

Ask your pharmacist how far apart to take them

Orlistat, a weight-loss medicine, reduces the absorption of fat-soluble vitamins, including vitamin D. Its label advises a daily multivitamin with vitamins A, D, E and K taken at a separate time from orlistat, and in its trials low vitamin D levels were more common on orlistat than on placebo.^1,4,5

On the medicine's label

Ask your pharmacist or doctor first

Bile acid sequestrants such as cholestyramine can block the absorption of fat-soluble vitamins, including vitamin D. The cholestyramine label lists low vitamin D among the effects of long-term use, and MedlinePlus lists vitamin D supplements among the products that interact with it.^6,7

On the medicine's label

Who should ask a doctor first

People with high blood calcium, kidney disease, kidney stones or an overactive parathyroid gland
Anyone pregnant or breastfeeding who wants more than the recommended amount
People with a digestive condition that limits fat absorption, or who have had weight-loss surgery, since they may need a tailored dose²
Anyone giving vitamin D to a baby or child, whose upper limits are lower¹
Anyone already taking prescription vitamin D

Counting every source

Vitamin D turns up in multivitamins, calcium supplements, cod liver oil and fortified foods. In our own range, the Vitamin D3 softgel (50 mcg), our immune formula (40 mcg), Ashwagandha Complex (20 mcg) and Men's Multi (10 mcg) all contain it, and all four together come to 120 mcg, over the 100 mcg adult limit.¹

What's in ours

What’s in ours

Vitamin D3: Vitamin D-3, 50 mcg (2,000 IU) per serving, from the label
Men's Multi: Vitamin D, 10 mcg per serving, from the label
Ashwagandha Complex: Vitamin D3, 20 mcg per serving, from the label
Immune Support: Vitamin D3, 40 mcg per serving, from the label

Questions people ask

Is it safe to take vitamin D3 every day?

Taking it daily is the normal way to take it, and the largest trials gave it every day for years. Keep your total at or below the 100 mcg (4,000 IU) upper limit from all sources, and ask your doctor before going higher.^1,3

Can you get too much vitamin D from the sun?

No. Your skin limits how much it makes. Tanning beds are different: frequent use can push blood levels very high.^1,2

Are vitamin D side effects different for women and men?

The limits and the signs of too much are the same. The sex-specific finding on this page comes from a trial in women after menopause, where calcium taken with vitamin D led to more kidney stones.²

Can vitamin D upset your stomach?

Not at normal doses: in VITAL, 2,000 IU a day caused no more stomach complaints than placebo. Nausea and vomiting are signs of far too much, usually from very high doses taken for a long time.^1,3

See what we make

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See the Full Measure line Ashwagandha Complex Immune Support Men's Multi

Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.