“The upper tolerable intake level for vitamin D in the general population has been set at 4000 international units (IU) daily, but considerable uncertainty remains.” “Our meta-analysis indicates that compared with placebo or low-dose (400 IU/d) vitamin D, a supplement of 3200–4000 IU vitamin D daily results in significantly higher risks of hypercalcemia (RR = 2.21, 95% CI: 1.26–3.87), falls (RR = 1.25, 95% CI: 1.01–1.25), and hospitalization (RR = 1.16, 95% CI: 1.01–1.33).” “In conclusion, supplemental daily vitamin D doses of 3200–4000 IU appear to increase the risk of hypercalcemia and some other adverse events in a small proportion of individuals, indicating that this dose is not completely safe.”

“The IOM report (20) recommended that the tolerable UL for vitamin D should be 1000 IU/d for children 0–6 months, 1500 IU/d for children 6 months to 1 yr, 2500 IU/d for children 1–3 yr, and 3000 IU/d for children 4–8 yr. For children 9 yr and older and all adults, they recommend that the UL be 4000 IU/d.” “Although no long-term studies have examined these higher doses of vitamin D on serum calcium levels, there are no reported cases of vitamin D intoxication in the literature to suggest that intakes of up to 4000 IU/d of vitamin D cause hypercalcemia. In healthy adults, 5 months of ingesting 10,000 IU/d of vitamin D neither caused hypercalcemia nor increased urinary calcium excretion, which is the most sensitive indicator for potential vitamin D intoxication.”

“Vitamin D toxicity can cause hypercalcemia, hypercalciuria, and high serum 25(OH)D concentrations; in extreme cases, it may lead to renal failure, calcification of soft tissues, cardiac arrhythmias, and death.” “The Tolerable Upper Intake Level for vitamin D ranges from 25 to 100 mcg (1,000–4,000 IU), depending on age.” “For adults 19–50 years: 100 mcg (4,000 IU). The UL is the maximum daily intake unlikely to cause adverse health effects.”

Vitamin D toxicity usually isn’t life-threatening, but it can be quite harmful to your health. Severe cases can cause issues such as kidney failure, abnormal heart rhythm (arrhythmia), unsteady gait (ataxia) and confusion. The symptoms of vitamin D toxicity are mainly due to hypercalcemia. They include: decrease in appetite, nausea and vomiting, constipation, dehydration, increased thirst, frequent urination, confusion, lethargy and fatigue, muscle weakness and difficulty walking, bone pain, kidney stones.

“In the clinical trials included in the systematic review, the vitamin D dosages ranged from 600 IU to 5000 IU (15 to 125 μg) daily equivalent, usually provided daily or weekly.” “Large RCTs show that supplementation with the doses of vitamin D3 summarized herein is safe and not generally associated with adverse outcomes such as hypercalcemia and kidney stones.” “Adults are recommended to consume the DRI through foods and/or a multivitamin or vitamin D supplement amounting to 600 IU (15 μg) for those 50–70 yr, and 800 IU (20 μg) for those ≥70 yr.”

“In the general adult population younger than age 50 years, we suggest against empiric vitamin D supplementation. Adults in this age group should follow the Recommended Daily Allowance established by the IOM (600 IU [15 µg] daily).” “In the general population aged 50 to 74 years, we suggest against routine vitamin D supplementation. Adults in this age group should follow the Recommended Daily Allowance established by the IOM (600 IU [15 μg] daily for those aged 50 to 70 years; 800 IU [20 μg] daily for those older than 70 years).” “In the clinical trials included in the systematic review, the vitamin D dosages ranged from 600 IU to 5000 IU (15 to 125 μg) daily equivalent, usually provided daily or weekly.”

“The panel suggests against empiric vitamin D supplementation above the current DRI to lower the risk of disease in healthy adults younger than 75 years.” “In the general adult population younger than age 50 years, we suggest against empiric vitamin D supplementation… Adults in this age group should follow the Recommended Daily Allowance established by the IOM (600 IU [15 µg] daily).” “In the clinical trials included in the systematic review, the vitamin D dosages ranged from 600 IU to 5000 IU (15 to 125 μg) daily equivalent, usually provided daily or weekly.” “In adults aged 50 years and older who have indications for vitamin D supplementation or treatment, we suggest daily, lower-dose vitamin D instead of nondaily, higher-dose vitamin D.”

“The good news is that, in a report issued by IOM on November 30, 2010, the RDA has now increased by 50% (from 400 IU to 600 IU) and the tolerable Upper Limit has now doubled (from 2,000 IU to 4,000 IU).” “The recommendations for individual consumption of vitamin D has now increased, as has the tolerable Upper Limit that indicates a higher intake level at which the vast majority of people will not suffer any unpleasant side effects.” “And the leeway for safe use at the upper end is now double what it was before, making such supplementation at higher levels still within a margin generally accepted as safe; at least up to 4,000 IU, though as usual that number is deliberately set low and has a large safety margin.”

“The FNB evaluated the potential for high intakes of vitamin D to produce adverse effects and set a safe Tolerable Upper Intake Level (UL) of 50 μg (2000 IU) for infants 0–6 months, and higher ULs up to 100 μg (4000 IU) for adults and children older than 8 years.” “The UL was based on the risk for hypercalcemia and, in some cases, hypercalciuria, and not on frank toxicity such as nephrocalcinosis.” “The UL is defined as the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population.”

“Healthy adults under the age of 75 are unlikely to benefit from taking more than the daily intake of vitamin D recommended by the Institutes of Medicine (IOM)… Key recommendations from the guideline include: We suggest against vitamin D supplements at doses beyond the reference dietary intakes recommended by the IOM in healthy adults under 75 years old.” “For children, pregnant people, adults older than 75 years and adults with high-risk prediabetes, the guideline recommends vitamin D higher than the IOM recommended daily allowance.”

Vitamin D3 supplementation at 4000 IU per day was safe and well tolerated among overweight/obese participants at high risk for diabetes. The overall frequency of protocol-specified AEs of interest, which included nephrolithiasis, hypercalcemia, hypercalciuria, or low estimated glomerular filtration rate, was low and did not differ by group. High-dose daily vitamin D3 supplementation at a dose of 4000 IU daily (considered the tolerable upper intake level for adults by the National Academy of Medicine) was well-tolerated and did not result in an increased risk of AEs or SAEs, including side effects that have been previously associated with vitamin D.

Supplemental vitamin D doses of 3200–4000 IU/d appear to increase the risk of hypercalcemia and some other adverse events in a small proportion of individuals. Since in our meta-analysis, 4 cases of hypercalcemia per 1000 individuals were vitamin D-induced, hypercalcemia at a daily dose of 3200–4000 IU has to be considered an occasional adverse event. These findings indicate that a daily dose of 3200–4000 IU is not completely safe, although the absolute risk increase is small.

“The doses used in the studies evaluated ranged from 600 to 5000 IU/day (15 to 125 μg), with an estimated average of 2500 IU (63 μg) per day.” “Healthy people should follow the DRI recommended by the IOM. The DRI is enough for individuals not in one of the high-risk groups described in the guideline. Supplementation with therapeutic doses of vitamin D may be needed if levels are low in people who are in one of the high-risk groups.” “For people at low-risk of low vitamin D, this guideline suggests the daily doses of vitamin D defined by the IOM. This includes those between 19 and 74 years of age who are not pregnant or pre-diabetic (600 IU daily for those aged between 19 and 69 years, and 800 IU for those aged between 70 and 74 years).”

There have been no cases of vitamin D3 induced hypercalcemia or any adverse events attributable to vitamin D3 supplementation in any patient. In summary, long-term supplementation with vitamin D3 in doses ranging from 5000 to 50,000 IUs/day appears to be safe.

Considering the excellent safety profile of vitamin D3 at a dose of 5000 IU/day, we did not include laboratory testing or other clinical interventions in our procedures unless clinically indicated. Among the 299 enrolled subjects, 182 workers in the intervention group reported at least 1 treatment-emergent adverse event. Laboratory tests (vitamin D, calcium, phosphorus, magnesium levels) were ordered for a total of 22 subjects. There were no instances of hypercalcemia reported. One subject reported nephrolithiasis on a survey 1 month after the event and was immediately withdrawn; the nephrolithiasis was considered unrelated to the study vitamin D3.

Daily intake of vitamin D varied between 5,000 IU and 50,000 IU. There have been no cases of vitamin D3-induced hypercalcemia or any adverse events attributable to vitamin D3 supplementation in any patient. No instances of hypercalcemia were reported from these doses of vitamin D over a period of up to seven years, and long-term vitamin D3 supplementation at doses between 5,000 and 50,000 IU appears to be safe in this cohort.

“Higher doses of vitamin D may be dangerous. Vitamin D doesn't dissolve in water, so it can't be excreted through urine; instead, excess vitamin D builds up in the body tissues and bloodstream.” “A study of older people already at risk for falls found an increased fall risk among those taking higher doses of vitamin D (50 mcg to 100 mcg, or 2,000 IU to 4,000 IU), compared with lower doses (6.3 to 25 mcg, or 250 IU to 1,000 IU).” “Unless your medical team recommends it, avoid taking more than 100 mcg (4,000 IU) per day, which is considered the safe upper limit.”

No adverse events with respect to treatment were reported in either arm. In this randomized trial comparing 5000 IU versus 1000 IU vitamin D3 daily for two weeks in deficient patients, there were no reports of treatment-related side effects. The study concluded that both dosing regimens were well tolerated over the short term.

“Taken in typical doses, vitamin D is thought to be mainly safe. But taking too much vitamin D in the form of supplements can be harmful and even deadly.” “Taking more than 4,000 IU a day of vitamin D might cause: Upset stomach and vomiting… Muscle weakness… Heart rhythm issues… Kidney stones and kidney damage.” “The recommended daily amount (RDA) of vitamin D for most adults is 600 IU a day. For adults 71 and older, the RDA is 800 IU a day.”

Even when taking high dose vitamin D supplements, it’s unlikely that a healthy person’s blood vitamin D levels would come close to reaching excessive or toxic levels. Symptoms of hypercalcemia include digestive distress, such as vomiting, nausea, constipation, and stomach pain; fatigue, dizziness, hallucinations, and confusion; loss of appetite; excessive urination; kidney stones, kidney injury, and even kidney failure; high blood pressure and abnormal heart rhythms; dehydration. In some cases, vitamin D toxicity can result in kidney injury and even kidney failure.

“The authors of this article consider a daily vitamin D supplement dose of 2000 IU as an effective and safe dose that may be suitable for the prevention and treatment of vitamin D deficiency in most adults.” “They note that while the Endocrine Society guideline recommends following IOM reference intakes for healthy adults under 75 years and does not support widespread high-dose supplementation, doses up to 4000 IU/day are regarded as the tolerable upper intake level in many expert documents.”

In this randomized clinical trial of vitamin D 5000 IU daily for patients with neuropathic pain, no adverse events occurred. Vitamin D levels and VAS pain scores were negatively correlated in the intervention group. The authors report that the 5000 IU dose was well tolerated over the study period without any recorded side effects.

“When taken by mouth: Vitamin D is likely safe when taken in recommended amounts. Most people don't experience side effects with vitamin D, unless too much is taken.” “Taking vitamin D for long periods of time in doses higher than 4000 IU (100 mcg) daily is possibly unsafe and may cause very high levels of calcium in the blood.” “Most people should not consume more than 4000 IU daily unless under the care of a healthcare provider.”

Most experts advise taking no more than 4,000 IU of vitamin D a day. Exceeding that on a regular basis, even if you are vitamin D deficient, could produce toxic levels that damage your health. With too much vitamin D, your blood calcium levels can rise to dangerous levels, causing nausea, vomiting and stomach pain. You may also experience excessive thirst and need to urinate more frequently. Excess calcium can bind with phosphates in your blood and form crystals that collect in your body’s soft tissues. In severe cases, it can lead to permanent kidney and lung damage.

Daily vitamin D3 at 5000 IU has held up well in multiple clinical trials lasting up to three years, with no alarming safety signals in monitored participants. The strongest safety evidence comes from a large randomized controlled trial in adults with prediabetes, where participants took 4000 IU daily for three years; that trial found no increase in kidney stones, hypercalcemia, or serious adverse events, and participants were allowed an additional 1000 IU on top of the study dose, bringing some to a total of 5000 IU per day, still without safety signals. A systematic review covering nearly 13,000 people taking 3200 to 4000 IU daily for six months or longer found a small but statistically significant increase in hypercalcemia and slightly more falls and hospitalizations, though kidney stones did not clearly increase.

“In adults aged 50 years and older with indications for vitamin D supplementation or treatment, the panel suggested daily, lower-dose vitamin D instead of intermittent use of high doses.” “The expert panel suggests children, pregnant persons, adults aged ≥75 years, and adults with prediabetes consume more vitamin D than the recommended daily allowance.” “In healthy individuals aged less than 75 years, the panel advised against empiric vitamin D supplementation, and instead recommended that they follow the IOM’s recommended daily allowance of 600 IU (15 μg).”

“This study aims to test if supplementation with high dose oral VitD (4,000 IU) will successfully correct VitD insufficiency, compared to treatment with standard dose oral VitD (600 IU).” “The Data Safety Monitoring Board for this study will review Adverse Events and all safety data collected every six months… The DSMB will be particularly concerned with falls and fractures, renal stones, hepatic/renal insufficiency, and achieving extremely high levels of VitD.” “Overall, we expect the tolerability of VitD supplementation to be excellent in this population, but will test if safety and aspects of health are superior/inferior in either of the treatment arms.”

However, excessive vitamin D can lead to dangerously high calcium levels in the blood, causing uncomfortable and potentially harmful symptoms. Signs of vitamin D toxicity or high calcium levels in the blood include: digestive issues such as vomiting, nausea, and stomach pain; fatigue, dizziness, and confusion; increased thirst; frequent urination. Frequent consumption of excessive vitamin D can lead to kidney damage. In fact, most studies have reported moderate to severe kidney damage in individuals with vitamin D toxicity.

“For empiric supplementation, daily, lower-dose vitamin D is preferred over non-daily, higher doses.” “In the clinical trials included in the SR that reported on adverse events, the vitamin D doses ranged from 600 to 5000 IU (15 to 125 μg) daily equivalent, usually provided daily or weekly.”

At a dosage of 5000 IU, it’s important to be aware of potential side effects, even though they are generally rare when taken as directed. While Vitamin D3 is essential, taking high doses like 5000 IU can lead to some side effects in certain individuals. Here are some of the most common ones: hypercalcemia (an elevated level of calcium in the blood, which can manifest as nausea, vomiting, and weakness); digestive issues such as stomach pain, constipation, or diarrhea; allergic reactions such as itching or rash can occur, though rare.

“Clinical science indicates that higher levels are still quite safe, at least up to 10,000 IU daily for most adults.” “According to a report in the journal Nutrition Reviews, ‘The input needed for efficacy, in addition to typical food and cutaneous inputs, will usually be 1000–2000 IU/day of supplemental cholecalciferol [vitamin D3]. Toxicity is associated only with excessive supplemental intake (usually well above 20,000 IU/day).’” “People have already been taking over 2,000 IU daily, the old tolerable Upper Limit, without apparent harm and will probably continue to take over the new 4,000 IU UL as well.”

They concluded that vitamin D supplementation levels greater than 1000 international units per day did not prevent falls compared with 200 international units per day. And doses greater than 2000 international units per day were potentially showing safety concerns. This randomized study also found that vitamin D doses of 4000 international units per day and 10,000 international units per day resulted in lower bone mineral density compared to 400 international units per day. The speaker notes that randomized trial data show that higher doses can increase the risk of certain problematic health outcomes, though the risk for any individual is probably pretty small.