Category: Calcium/Bone Disorders

Monitor: 28

28 - Sublingual vitamin D effective in improving low vitamin D levels in patients resistant to conventional vitamin D supplementation

Thursday, Apr 25
12:30 PM – 1:00 PM

Objective :

Vitamin D plays a major role in the regulation of calcium and phosphorus levels in the body, with its deficiency leading to osteomalacia and rickets. Vitamin D deficiency is quite prevalent worldwide and is typically treated with oral supplementation. We hereby report a patient with severe vitamin D deficiency in the absence of other known risk factors who was resistant to oral supplementation and finally responded to sublingual vitamin D3 supplementation in high doses. 

Methods : /

Results :


Discussion :

66-year old female with previous history of osteoporosis who presented for initial evaluation of low vitamin D levels with a 25(OH)D level of 16 ng/ml. She did not have a prior history of gastric surgeries, intestinal surgeries, or malabsorptive conditions. She denied complaints of diarrhea or flatulence. She had taken alendronate previously for 5 years for osteoporosis and was on drug holiday since 2011. She was initially treated with vitamin D3, 2000 IU daily without improvement and then initiated on vitamin D2 50,000 IU weekly supplementation. Subsequent 25(OH)D level 8 weeks later was 14 ng/ml. Workup for celiac disease was negative with normal tissue transglutaminase antibodies. Patient was advised to squirt vitamin D2 sublingually after puncturing vitamin D2 gel caps weekly to see if absorption improved.  Lab testing 8 weeks later revealed mild improvement in 25 (OH)D levels to 23 ng/ml. As 25(OH)D level was still below target, she was asked to change to vitamin D3 drops instead of vitamin D2, at 4000 units daily, administered sublingually. Repeat 25(OH)D level was 24 ng/ml, therefore the dose of vitamin D drops was increased to 4000 units twice daily with improvement in 25(OH)D level to 28 ng/ml. All this time, urine calcium/Cr ratio remained below 50 mg/g Cr despite the fact that she was having 4 glasses milk a day. Upper endoscopy was done with duodenal biopsies to evaluate for celiac, which were negative. She was maintained on this regimen, and the 25(OH)D level a year later remained stable at 36 ng/ml. 

Various preparations are available for vitamin D supplementation of which the commonly used forms are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). There are few case reports of vitamin D deficiency correction with sublingual administration of vitamin D2. However, not much is known about the pharmacokinetics of sublingual vitamin D3 absorption.

Conclusion :

Further studies are needed to help understand the pharmacokinetics of sublingual vitamin D3 absorption; as this may be an effective alternative mode of vitamin D supplementation in patients with poor oral vitamin D absorption, despite aggressive supplementation.


Sobia Faisal

UConn Internal Medicine, Connecticut

Resident physician

Faryal S. Mirza

Attending Physician
Uconn Endocrinology

Attending physician, UConn Endocrinology

Sobia Faisal

UConn Internal Medicine, Connecticut

Resident physician