Verified Supplement Data Primary-sourced

Vitamin D Side Effects: Too Much, Toxicity and the Signs

By Erin Rose · Published · Reviewed against primary sources · Methodology · About Us

Informational summary of published trials, case series, product labels and the NIH fact sheet, not medical advice or a diagnosis. Vomiting, confusion, severe weakness or a sharp drop in urine output in someone taking high-dose vitamin D is a reason to call a clinician the same day, not to keep reading.

Quick answer

The side effects people report from vitamin D are the symptoms of high blood calcium, which is what a sustained excess of vitamin D produces: nausea, loss of appetite, constipation, thirst, frequent urination, muscle weakness, and confusion, with kidney stones behind them. The threshold that matters is not a pill size but a blood level held over time: toxicity is defined as a serum 25(OH)D above 150 ng/mL (375 nmol/L) with hypercalcemia, and every published case with a known dose involved at least 40,000 IU a day, usually for months.

The shelf sells above the ceiling more often than you would guess. We read 948 of the 29,277 vitamin D labels filed with the NIH. Of the 905 that state a daily direction, 152 (16.8%) tell you to take more than the 4,000 IU upper limit every day. See what the shelf sells →

Toxicity threshold, serum 25(OH)D>150 ng/mLwith hypercalcemia; 375 nmol/L
Mild hypercalcemia at 10,000 IU/day for 3 years9%vs 0% at 400 IU, Billington 2020
Labels directing above the 4,000 IU limit 152 of 905 our census of 948 labels, 2026-09-16

Working out what to take rather than what went wrong? The vitamin D dosage guide lists the NIH intake ranges, and this page stays on what too much does →

On this page
  1. Common side effects, and at what dose
  2. Serious effects and who is at risk
  3. Interactions worth knowing
  4. What the shelf sells
  5. What to do
  6. FAQ

Common side effects, and the dose each one shows up at

How to read this Every figure below carries its dose, duration and trial. A side effect at 10,000 IU a day for three years is not evidence about 1,000 IU for a month.

At ordinary doses the honest answer is that most people get nothing. The clearest evidence is a three-year Calgary trial that randomised 373 healthy adults aged 55 to 70 to 400, 4,000 or 10,000 IU of D3 a day and then went looking for harm. Clinical adverse events were reported by almost everyone in all three arms and were balanced across them. What separated by dose were two laboratory findings (Billington 2020, PMID: 31746327).

Side effects of vitamin D by dose, with the trial or review each figure came from and the duration it was measured over.
EffectWhat the evidence showsDose and duration
Hypercalciuria (extra calcium in the urine) The most common finding by a wide margin: 87 of 373 participants (23%), rising from 17% at 400 IU to 22% at 4,000 and 31% at 10,000 (Billington 2020, PMID: 31746327). Across 14 long-term trials the risk ratio was 1.64 against placebo (Malihi 2016, PMID: 27604776). 400–10,000 IU/day, 3 years
Mild hypercalcemia (raised blood calcium) 15 of 373 participants (4%): 0% at 400 IU, 3% at 4,000 and 9% at 10,000. Every case was mild and resolved on repeat testing (Billington 2020). Pooled across 37 long-term trials the risk ratio was 1.54 (Malihi 2016). 400–10,000 IU/day, 3 years
Nausea, vomiting, loss of appetite, constipation These are hypercalcemia symptoms rather than direct effects of the vitamin, and they appear in the toxicity case series, not in the dose-ranging trials (NIH Office of Dietary Supplements; Marcinowska-Suchowierska 2018, PMID: 30294301). Sustained mega-doses
Excessive thirst, frequent urination, dehydration Same mechanism: high calcium impairs the kidney's ability to concentrate urine. Listed by the ODS and present across the case series (Kaur 2015, PMID: 26053339). Sustained mega-doses
Kidney stones Not shown for vitamin D alone. Across nine long-term trials the risk ratio was 0.66, favouring vitamin D and not statistically significant (Malihi 2016), and a later review of 32 trials at 2,800 IU a day or more found no increase either (Malihi 2019, PMID: 30529281). Stones did rise when a calcium supplement was added: see the interactions section. 2,800 IU/day and up, 1 year or longer
Falls and fractures on very large intermittent doses A single 500,000 IU dose each autumn raised falls (rate ratio 1.15) and fractures (1.26) in 2,256 women aged 70 and over (Sanders 2010, PMID: 20460620). Monthly 60,000 IU produced more falls than monthly 24,000 IU (66.9% vs 47.9%) in 200 adults with a prior fall (Bischoff-Ferrari 2016, PMID: 26747333). Annual or monthly bolus dosing
Lower bone density at high daily doses The opposite of the intended effect: radial bone density fell 1.2% at 400 IU, 2.4% at 4,000 and 3.5% at 10,000 over three years in 311 adults, with no difference in bone strength (Burt 2019, PMID: 31454046). 3 years of daily dosing

Two things follow. A person on 1,000 or 2,000 IU a day who feels unwell almost certainly has a different explanation, and the useful move is to look for one. And above the upper limit the trade-off stops being free: the calcium findings climb with dose while the bone benefit the high dose was taken for does not arrive.

Serious effects: what toxicity actually looks like, and who gets there

Vitamin D toxicity is rare, and when it happens it is hypercalcemia. Vitamin D raises calcium absorption in the gut; at supraphysiological concentrations, 25(OH)D itself binds the vitamin D receptor and pushes that absorption past what the body can regulate, producing marked hypercalcemia and hypercalciuria (Tebben 2016, PMID: 27588937). The NIH Office of Dietary Supplements puts the picture as a total calcium above 11.1 mg/dL against a normal range of 8.4 to 10.2, together with a serum 25(OH)D typically above 375 nmol/L (150 ng/mL). High calcium is a reason to see a clinician.

A high blood level is not the same as toxicity. In a ten-year review of 20,308 vitamin D tests in one US county, 1,714 people (8.4%) had a 25(OH)D above 50 ng/mL and 37 were at or above 100, yet only 4 had a hypercalcemia that could be linked in time, and 1 had clinical toxicity, at 364 ng/mL (Dudenkov 2015, PMID: 25939935). High levels became far more common over the decade without a matching rise in acute toxicity. A number above the reference range is a reason to recheck and to look at the dose, not a diagnosis.

The dose that gets people there is much higher than the upper limit suggests. Reviewing every published case with a known dose, Vieth found all of them involved at least 40,000 IU a day, and no adverse effect below a 25(OH)D of 140 nmol/L (Vieth 1999, PMID: 10232622). Applying the Food and Nutrition Board's own risk-assessment method, Hathcock argued for 10,000 IU a day as the level supported by the absence of toxicity in healthy adults (Hathcock 2007, PMID: 17209171); the Board itself says signs of toxicity are unlikely below that figure, while keeping the adult upper limit at 4,000 IU as a population ceiling with margin built in.

The three realistic routes

Mega-dose regimens, usually prescribed. At one Indian referral centre, 16 patients presented with vitamin D toxicity over two years. Their median 25(OH)D was 371 ng/mL (range 175 to 1,161), median calcium 13 mg/dL, and median cumulative dose 3,600,000 IU. Prescribed mega-doses caused every single case (Kaur 2015, PMID: 26053339). A review of 13 published case reports found the same pattern, with 25(OH)D between 150 to 1,220 ng/mL and calcium between 11.1 to 23.1 mg/dL, from manufacturing errors and from overdosing by patients or prescribers (Galior 2018, PMID: 30042334). Around 75% of published intoxication reports have appeared since 2010, and most were preventable (Taylor 2018, PMID: 29498758).

A product that does not contain what the label says. Two US patients reached severe hypercalcemia after manufacturing and labeling errors left them consuming more than 1,000 times the recommended daily dose; it took about 1 year for their 25(OH)D to come back down (Araki 2011, PMID: 21917864). At one New York hospital, 9 patients presented with hypercalcemia after taking a single over-the-counter preparation whose label claimed 600,000 IU per vial; laboratory analysis found 864,000 IU of D3 (Lowe 2011, PMID: 21123442). Their calcium ran from 10.8 to 17.2 mg/dL. You cannot inspect your way around this one; what you can do is buy from brands that submit to third-party testing, which is the only part of the problem a shopper controls.

Stacking without adding it up. Vitamin D appears in a standalone bottle, in most multivitamins, in calcium and bone formulas, in prenatals, in fish oil blends and in fortified milk. Each is modest; the total is not necessarily. About 3% of US adults report taking at least 4,000 IU a day, and use above both 1,000 and 4,000 IU rose across the 1999 to 2014 national surveys (Burt 2019; Rooney 2017, PMID: 28632857). Add up every label in the cupboard before deciding your dose is fine.

Who is at genuine risk at ordinary doses

For a small group a normal dose is not a normal dose, because their bodies make the active hormone outside the kidney's control, or already run their calcium high.

  • Sarcoidosis, tuberculosis and other granulomatous disease, and some lymphomas. Macrophages or tumour cells express the enzyme that converts 25(OH)D to the active hormone, and that conversion is substrate-driven rather than regulated (Tebben 2016). The evidence is not "never supplement": in the studies reviewed, mean serum calcium did not change with supplementation, though hypercalciuria turned up in 1 of 13 patients in one study and 2 of 16 in another, and lower vitamin D levels track with more severe disease (Gianella 2020, PMID: 33659946). A 2026 review in Chest works through the same dilemma case by case (Ungprasert 2026, PMID: 42242548). The rule is supervision with calcium monitoring, not avoidance.
  • Primary hyperparathyroidism or any history of high blood calcium. The regulator that normally holds calcium down is the thing that is broken, so the usual brake on absorption is missing.
  • Kidney disease, or a history of calcium kidney stones. The kidney is what clears the excess calcium and what pays for hypercalciuria.
  • Infants and young children. Adult drops in a child's mouth is a real route to trouble, and dosing here belongs to a pediatrician.
  • Pregnancy and breastfeeding. The same 4,000 IU upper limit applies from age 19 (NIH ODS), and calcium handling in pregnancy is its own subject, so the dose belongs with the prenatal team. Our vitamin D for women page covers what prenatal labels carry.

Hypercalcemia from all causes reaches up to 4% of the population (Tebben 2016), and most of it is not vitamin D. If your calcium is high, the workup looks for hyperparathyroidism and malignancy as well as for your supplement.

Interactions worth knowing

The NIH Office of Dietary Supplements names four drug classes on the vitamin D fact sheet. Two change how much vitamin D you end up with; two change what a given amount does to your calcium.

Drug and supplement interactions with vitamin D, the direction of each, and what to do about it.
WhatDirectionEvidenceWhat to do
Thiazide diuretics (hydrochlorothiazide, chlorthalidone, indapamide) Raises calcium: the drug cuts urinary calcium loss while vitamin D raises gut absorption. The ODS flags the combination as a hypercalcemia risk, especially in older adults and in people with reduced kidney function or hyperparathyroidism. In 328 adults given up to 4,000 IU for three months, hydrochlorothiazide users ended 0.2 mg/dL higher on calcium, with 1 of 84 hypercalcemic against 0 of 44 (Chandler 2014, PMID: 24657333). Separately, 221 county residents developed thiazide-associated hypercalcemia a mean 5.2 years after starting, and 24% proved to have primary hyperparathyroidism underneath (Griebeler 2016, PMID: 26751196). Ask the prescriber whether calcium checks make sense. A high calcium on a thiazide deserves a parathyroid workup.
Calcium supplements Raises stone risk when both are taken together. In the Women's Health Initiative, 36,282 postmenopausal women took 1,000 mg of calcium plus 400 IU of D3 daily for 7 years. Hip bone density rose slightly, hip fracture did not fall significantly, and kidney stones rose: hazard ratio 1.17 (1.02 to 1.34) (Jackson 2006, PMID: 16481635). That was at a vitamin D dose well under the limit, so this is about the pairing, not the dose. Check whether you need supplemental calcium at all before adding it to vitamin D. Dietary calcium was not what raised the risk.
Digoxin Raises the consequence of a rising calcium. The FDA label for digoxin lists hypercalcemia, along with low body weight, advanced age, impaired kidney function, low potassium and low magnesium, among the states that may predispose to digoxin toxicity (FDA prescribing information, DailyMed). Dose and monitoring belong to the prescriber. Do not add a high-dose vitamin D on your own while on digoxin.
Corticosteroids (prednisone and similar, long term) Lowers vitamin D: reduces calcium absorption and impairs vitamin D metabolism. In NHANES 2001–2006, deficiency below 25 nmol/L was more than twice as common in oral steroid users (11%) as in non-users (5%) (NIH ODS). Ask the prescriber about vitamin D and bone monitoring.
Orlistat (Xenical, alli) Lowers vitamin D: blocks absorption of a fat-soluble vitamin. The ODS notes that orlistat with a reduced-fat diet can reduce absorption of vitamin D from both food and supplements, lowering 25(OH)D. Ask a clinician about testing.
Statins Two-way and modest. The ODS notes statins may reduce endogenous vitamin D synthesis, and that high supplemental vitamin D might reduce the potency of atorvastatin, lovastatin and simvastatin, because they compete for the same metabolising enzyme. Worth mentioning at a medication review.

Two claims listed elsewhere are left out because we could not source them to a record we would print: bile-acid binders such as cholestyramine, and vitamin K2 as protection against vitamin D toxicity. We found no human trial showing that adding K2 prevents hypercalcemia from a high vitamin D intake, so we do not repeat it; our K2 page covers what the human evidence supports.

We read 948 labels: 152 of the 905 with a daily direction exceed the upper limit

Original research Every on-market vitamin D supplement label in the NIH Dietary Supplement Label Database whose product name carries the term (29,277 on the market, 948 read, 936 with a parseable quantity, 905 with a daily direction, 274 brands), dose taken from the Supplement Facts panel and multiplied by the servings the label directs.

The middle of the shelf is unremarkable. The median label directs 1,000 IU a day, a quarter of the 4,000 IU upper limit. The tail is long: the 90th percentile label directs 5,000 IU and the highest 50,000 IU, a dose that belongs to a prescription schedule and is being sold as a bottle. Of the 905 labels stating a daily direction, 152 of them, 16.8%, tell you to take more than the upper limit every day.

Vitamin D a label tells you to take per day, against the adult upper limit
0 1500 3000 4500 6000 Median label of 905 with a direction 1,000 IU Adult upper limit Food and Nutrition Board 4,000 IU 90th percentile label 152 cross the limit 5,000 IU
The median vitamin D label directs 1,000 IU a day, well under the 4,000 IU upper intake level, but the top tenth of the shelf directs 5,000 IU or more, above it. 152 of the 905 labels that state a daily direction cross the limit. Source: NIH Dietary Supplement Label Database, 948 vitamin D labels retrieved 2026-09-16, of which 905 state a daily direction; upper limit from the Food and Nutrition Board via the NIH Office of Dietary Supplements.
Vitamin D a label tells you to take per day, against the adult upper limit
ItemValue
Median label1,000 IU
Adult upper limit4,000 IU
90th percentile label5,000 IU

Two descriptive counts fill in the shape. By declared form, 835 labels declare D3 (cholecalciferol) and 49 declare D2 (ergocalciferol); the shelf is overwhelmingly D3, and the toxicity literature involves both. And 740 labels direct a single serving a day, which is why the median as directed and the median per serving land on the same 1,000 IU. That last point is the one finding from this census that survived our own split-half check.

What the census does not say matters as much. On this shelf the median dose as directed and the median per serving are the same 1,000 IU.

Method: 948 labels retrieved from the NIH Dietary Supplement Label Database (DSLD) v9 on 2026-09-16 for the term “vitamin d”, out of 29,277 on the market; 936 declare a parseable vitamin D quantity and 905 state a daily serving direction, which is the denominator for every share above. 7 labels above the plausibility ceiling of 100,000 IU were excluded. What it cannot tell you: which products sell most, whether the capsule matches the panel, or anything about products not filed with the NIH.

What the FDA adverse-event file says, and what it does not

The FDA's adverse-event system holds 3,425 reports naming vitamin D. The top reported reactions are Choking, Diarrhoea, Dysphagia, Nausea, Dyspnoea. Hypercalcemia does not appear among them at all. The most frequently reported reactions are swallowing events: choking and difficulty swallowing, alongside gastrointestinal upset.

That is an observation about a pile of reports, not a measurement of risk. These are voluntary reports with no denominator, so a share of reports can never be turned into a rate of harm, and a widely sold supplement accumulates reports for being widely sold. The pattern most plausibly reflects something physical: vitamin D is often a large softgel or a chalky tablet sold to older adults, and a large pill is a choking risk whatever is inside it. If swallowing is your actual problem, ask a pharmacist or clinician about a smaller or liquid format. What the file does not show is a stream of hypercalcemia reports.

What to do, tied to what you have

Each row is a symptom or a situation, not a dose. The NIH ranges are in the dosage guide.

  • Vomiting, confusion, severe weakness, or a large change in how much you drink and urinate, on a high dose. Stop the vitamin D and call a clinician today, asking about a serum calcium.
  • Nausea, constipation, unusual thirst on 5,000 IU or more, with no recent blood test. Talk to a clinician about a 25(OH)D and a calcium test, and take the bottles with you. The 25(OH)D test guide explains how the result is read.
  • No symptoms, but you are above the 4,000 IU limit and have been for months. The most common situation, and not an emergency. Add up every source, including the multivitamin and any bone or prenatal formula, and ask a clinician about your total. The 1,000 vs 5,000 IU comparison covers the label doses.
  • Choking, gagging or a stuck feeling on the capsule. Switch the format rather than the dose: a liquid, a spray or a small softgel delivers the same vitamin D without the pill.
  • You are on a thiazide diuretic, digoxin, long-term steroids or orlistat. Keep taking your medicine and raise the vitamin D dose with whoever prescribes, so a calcium check goes on the schedule.
  • You have sarcoidosis, another granulomatous disease, primary hyperparathyroidism, kidney disease or a history of calcium stones. Do not set your own dose; ask your clinician about vitamin D and monitoring (Gianella 2020).
  • You are taking a weekly or monthly bolus. Ask whether a daily dose would do the same job. The bolus trials are where the fall and fracture signals turned up (Sanders 2010; Bischoff-Ferrari 2016), and the 2024 Endocrine Society guideline favours daily over intermittent dosing (Demay 2024, PMID: 38828931).

The product links below go to Amazon and we may earn a commission if you buy. It never changes which product we pick or what we say about it. How we choose.

A 2,000 IU softgel: Nature Made Vitamin D3 2000 IU $0.08/day sits at half the upper limit and is registry-confirmed USP Verified.

A 1,000 IU softgel: Nordic Naturals Vitamin D3 1000 IU $0.13/day is at the median of the whole shelf, 1,000 IU, and a quarter of the limit.

Check price → · every pick is compared in the best vitamin D guide.

Frequently asked questions

What are the symptoms of too much vitamin D?

They are the symptoms of high blood calcium, not of the vitamin itself: nausea, vomiting, loss of appetite, constipation, excessive thirst, frequent urination, dehydration, muscle weakness, pain and confusion, with kidney stones downstream (NIH Office of Dietary Supplements; Marcinowska-Suchowierska 2018). In a series of 16 patients the presenting complaints were nausea, vomiting, altered awareness, constipation, pancreatitis, acute kidney injury and weight loss. None is specific to vitamin D, so a serum calcium settles it, not a symptom checklist.

How much vitamin D is too much?

The tolerable upper intake level for adults is 4,000 IU a day, a population ceiling with a wide margin rather than the dose at which harm starts. The Food and Nutrition Board says signs of toxicity are unlikely below 10,000 IU a day, and every published toxicity case with a known dose involved at least 40,000 IU a day (Vieth 1999). Duration is the other half: the 16 patients in the Indian series had taken a median cumulative 3,600,000 IU. A short course at 5,000 IU is a different thing from five years of it, which is why the answer is a blood test.

Can you get vitamin D toxicity from the sun?

Sunlight alone is not believed to cause it. Sunlight converts previtamin D3 in the skin into inactive forms once production has run far enough, which caps how much your skin can make. The NIH Office of Dietary Supplements states that experts do not believe excessive sun exposure causes vitamin D toxicity for that reason, while noting that frequent tanning-bed use can push 25(OH)D well above the toxic range. Documented toxicity traces to swallowed doses: mega-dose regimens, prescribing errors, and manufacturing or labeling errors.

What blood level counts as vitamin D toxicity?

A serum 25(OH)D above 150 ng/mL (375 nmol/L) together with hypercalcemia is the working definition (Marcinowska-Suchowierska 2018; NIH ODS). A high level on its own is not the same as toxicity: in a ten-year review of 20,308 tests in one US county, 1,714 people (8.4%) were above 50 ng/mL and 37 above 100, yet only 4 had an associated hypercalcemia and 1 had clinical toxicity (Dudenkov 2015). The Food and Nutrition Board still suggests avoiding levels above roughly 125 to 150 nmol/L.

Does vitamin D interact with medicines?

Some medicines change how vitamin D affects calcium. Tell your clinician or pharmacist about every supplement you take, and ask whether a calcium check makes sense for you.

Is 5,000 IU of vitamin D a day above the upper limit?

It is above the 4,000 IU upper limit and below the level at which documented toxicity occurs. The three-year Calgary trial gives the closest evidence: at 4,000 IU a day, mild hypercalcemia appeared in 3% of participants and hypercalciuria in 22%, against 0% and 17% at 400 IU, and every hypercalcemia resolved on a repeat test (Billington 2020). The same trial found radial bone density fell more at the higher doses, not less (Burt 2019). If you are at 5,000 IU with no recent blood test, talk to a clinician.

Do I need to stop vitamin D before surgery or a blood test?

Tell the team what you take and at what dose, because vitamin D changes the calcium result they will read. Whether to pause it is a decision for your clinician. If you are on a thiazide diuretic, digoxin, long-term steroids or orlistat, or you have sarcoidosis, primary hyperparathyroidism, kidney disease or a history of calcium kidney stones, your dose is a clinical decision rather than a shelf decision. The FDA label for digoxin lists hypercalcemia among the states that predispose to digoxin toxicity.

Related guides

Sources

  1. NIH Office of Dietary Supplements. "Vitamin D: Fact Sheet for Health Professionals." Tolerable upper intake levels by age, the definition and consequences of toxicity, the sun-exposure limit, and the orlistat, statin, steroid and thiazide interactions quoted on this page. ods.od.nih.gov
  2. Marcinowska-Suchowierska E, et al. "Vitamin D Toxicity-A Clinical Perspective." Front Endocrinol. 2018. PMID: 30294301
  3. Tebben PJ, et al. "Vitamin D-Mediated Hypercalcemia: Mechanisms, Diagnosis, and Treatment." Endocr Rev. 2016. PMID: 27588937
  4. Billington EO, et al. "Safety of High-Dose Vitamin D Supplementation: Secondary Analysis of a Randomized Controlled Trial." J Clin Endocrinol Metab. 2020. PMID: 31746327
  5. Burt LA, et al. "Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial." JAMA. 2019. PMID: 31454046
  6. Malihi Z, et al. "Hypercalcemia, hypercalciuria, and kidney stones in long-term studies of vitamin D supplementation: a systematic review and meta-analysis." Am J Clin Nutr. 2016. PMID: 27604776
  7. Malihi Z, et al. "Adverse events from large dose vitamin D supplementation taken for one year or longer." J Steroid Biochem Mol Biol. 2019. PMID: 30529281
  8. Vieth R. "Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety." Am J Clin Nutr. 1999. PMID: 10232622
  9. Hathcock JN, et al. "Risk assessment for vitamin D." Am J Clin Nutr. 2007. PMID: 17209171
  10. Kaur P, et al. "Vitamin D toxicity resulting from overzealous correction of vitamin D deficiency." Clin Endocrinol (Oxf). 2015. PMID: 26053339
  11. Galior K, et al. "Development of Vitamin D Toxicity from Overcorrection of Vitamin D Deficiency: A Review of Case Reports." Nutrients. 2018. PMID: 30042334
  12. Taylor PN, Davies JS. "A review of the growing risk of vitamin D toxicity from inappropriate practice." Br J Clin Pharmacol. 2018. PMID: 29498758
  13. Araki T, et al. "Vitamin D intoxication with severe hypercalcemia due to manufacturing and labeling errors of two dietary supplements made in the United States." J Clin Endocrinol Metab. 2011. PMID: 21917864
  14. Lowe H, et al. "Vitamin D toxicity due to a commonly available 'over the counter' remedy from the Dominican Republic." J Clin Endocrinol Metab. 2011. PMID: 21123442
  15. Dudenkov DV, et al. "Changing Incidence of Serum 25-Hydroxyvitamin D Values Above 50 ng/mL: A 10-Year Population-Based Study." Mayo Clin Proc. 2015. PMID: 25939935
  16. Jackson RD, et al. "Calcium plus vitamin D supplementation and the risk of fractures." N Engl J Med. 2006. PMID: 16481635
  17. Chandler PD, et al. "Risk of hypercalcemia in blacks taking hydrochlorothiazide and vitamin D." Am J Med. 2014. PMID: 24657333
  18. Griebeler ML, et al. "Thiazide-Associated Hypercalcemia: Incidence and Association With Primary Hyperparathyroidism Over Two Decades." J Clin Endocrinol Metab. 2016. PMID: 26751196
  19. Gianella F, et al. "The role of vitamin D in sarcoidosis." Fac Rev. 2020. PMID: 33659946
  20. Ungprasert P, et al. "Calcium and Vitamin D Supplements in Patients With Sarcoidosis." Chest. 2026. PMID: 42242548
  21. Sanders KM, et al. "Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial." JAMA. 2010. PMID: 20460620
  22. Bischoff-Ferrari HA, et al. "Monthly High-Dose Vitamin D Treatment for the Prevention of Functional Decline: A Randomized Clinical Trial." JAMA Intern Med. 2016. PMID: 26747333
  23. Rooney MR, et al. "Trends in Use of High-Dose Vitamin D Supplements Exceeding 1000 or 4000 International Units Daily, 1999-2014." JAMA. 2017. PMID: 28632857
  24. Demay MB, et al. "Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline." J Clin Endocrinol Metab. 2024. PMID: 38828931
  25. US Food and Drug Administration. Digoxin tablets, prescribing information (states that predispose to digoxin toxicity). DailyMed
  26. US Food and Drug Administration. CFSAN Adverse Event Reporting System (CAERS), the source of the vitamin D report counts and reaction ranking above. Voluntary reports with no denominator. Verified Supplement Evidence Database
  27. NIH Office of Dietary Supplements. Dietary Supplement Label Database. dsld.od.nih.gov (vitamin D labels retrieved 2026-09-16; only figures that recomputed in both halves of the read order are published here).