A 39-year-old male was referred to my practice by his mother who was concerned over his overzealous consumption of vitamin D.

The patient reported that, during the early months of the pandemic he began taking high doses of vitamin D because he had read that “Dr. Fauci recommended it.”

He claims to have taken four capsules of vitamin D twice daily for four days per week (he did not take vitamins on weekends). When I asked him the potency of the vitamin D supplements, he showed me a picture on his iPhone which indicated each capsule delivered 5000 International Units (125 mcg) of vitamin D3.

He had been doing this consistently since April or May and, at the time of our visit, at the end of December, had only stopped taking it for two or three days.

I calculated that this meant he had been taking in excess of 22,000 IUs of vitamin D per day, on average, for eight or nine months.

The patient had no complaints and stated he was in excellent health. He was a runner and completed three-to-six-mile runs three times weekly on average, sidelined only by occasional hip flexor soreness.

He denied fatigue, generalized muscle aches, headaches, flank pain, or changes in appetite or thirst. His physical exam was unremarkable.

He was instructed to stop taking vitamin D for the time being and to hydrate well. Blood and urine tests were performed

Discussion: Hypervitaminosis D is occasionally described in patients taking as little as 10,000 IU per day over sustained periods. One case report of a 73-year-old male with congestive heart failure taking that dose for many years revealed incipient renal failure with a creatinine of 7.43 and a serum calcium of 12.3 (normal = less than 10.6).¹ The patient’s creatinine and calcium normalized within 28 days after aggressive hydration and cessation of vitamin D.

Of course, compromised renal, or hepatic function are predisposing factors for hypervitaminosis D. So, too, are certain conditions: hyperparathyroidism, tuberculosis, sarcoidosis, and histoplasmosis, all of which affect calcium metabolism.

Symptoms of vitamin D excess resemble those of hypercalcemia²:

• Fatigue
• Loss of appetite
• Weight loss
• Excessive thirst
• Excessive urination
• Dehydration
• Constipation
• Irritability, nervousness
• Ringing in the ear (tinnitus)
• Muscle weakness
• Nausea, vomiting
• Dizziness
• Confusion, disorientation
• High blood pressure
• Heart arrhythmias

Long-term consequences of prolonged hypervitaminosis D may include the following:

• Kidney stones
• Kidney damage
• Kidney failure
• Osteoporosis
• Calcification (hardening) or arteries and soft tissues

The tolerable upper limit, or the maximum daily intake of vitamin D that is unlikely to result in any health risks, has been set at 4,000 IUs per day, but in my experience some patients require more to achieve optimal levels of vitamin D, and do so safely. I have never encountered a genuine case of vitamin D toxicity, although I’ve advised some patients to cut back when their blood levels surpassed the normal threshold.

Nevertheless, the specter of vitamin D excess looms, especially for patients taking multiple supplements simultaneously, each of which contain vitamin D, as when someone takes a multi, a bone support formula, and an immune supplement, along with additional D.

Results: The blood and urine tests for this patient were all within normal range. His renal function was unaffected. He showed no evidence of hypercalcemia, with neither serum nor ionized calcium elevations. His parathyroid hormone, as might be expected, was in the low normal range. There was no evidence of excess urine calcium or the presence of crystals that would signal risk for kidney stones.

Unsurprisingly, his 25OH vitamin D clocked in at 97 ng/ml, which is close to the lab’s upper limit of 100 ng/ml; the 1,25OH vitamin D was 72 pg/ml, which was near the top threshold of 75 pg/ml (reference values vary from lab to lab). But these values did not reach the toxic range.

Take-home: While the risk of vitamin D toxicity is real, especially when vitamin D’s benefits are so widely touted, this case suggests that, especially for young healthy individuals, there’s a significant margin for error. High-dose vitamin D supplementation is not without risks, especially in patients with comorbidities, so it is advisable to frequently monitor renal function, calcium and D levels, and to suspect overzealous supplementation if a patient presents with symptoms suggestive of hypervitaminosis D.

References

1. Sharma N, Landsberg E, Kumar V, et al. A Curious Case of Hypervitaminosis D. Cureus. June 8, 2020;12(6): e8515.
2. https://www.medicalnewstoday.com/articles/318415