Table 1 Wide variability in Vitamin D dose and duration, type of patients enrolled, and whether anemia was present or not in randomized clinical trials

Trautveffer 2014

Healthy adults

No

Fortified bread with 400 IU vit D3 daily

8 weeks

22,400 IU vit D3

Miskulin 2016^a

Adults with CKD

Yes

Oral dose of 50,000 IU vit D2 weekly

6 months

1,200,000 IU vit D2

Toxqui 2013

Adult Women

Yes

Fortified milk with 200 IU vit D3 & 15 mg iron daily

16 weeks

22,400 IU vit D3

Sooragonda 2015

Healthy adults

Yes

0.6 Lakh Amp vit D3+ Amp iron once

Once

600,000 IU vit D3

Smith 2017 [7]^a

Healthy adults

No

Oral dose of 250,000 IU, vit D3 once

Once

250,000 IU vit D3

Smith 2018 [6]

Critically ill adults

Yes

Enteral dose of 50,000 IU (I1) or 100,000 IU (I2) vit D3 daily

5 days

500,000 IU (I1) vit D3

250,000 IU (I2) vit D3

Madar 2016

Healthy adults

No

I1 = tablet 1000 IU, vit D3 daily

I2 = tablet 400 IU, vit D3 daily

16 weeks

42,000 IU (I1) vit D3

16,800 IU (I2) vit D3

Hennigar 2016

Healthy adults

No

Fortified bar with 1000 IU vit D3 + 2000 mg calcium, 2 bars per day

9 weeks

126,000 IU vit D3

Ernest 2016

Adults with hypertension

No

Oral dose of 2800 IU vit D3 daily

8 weeks

156,800 IU vit D3

Ernest 2017

Adults with heart failure

Some (23 of 172)

Oral dose of 4000 IU vit D3 daily

36 months

4,032,000 IU vit D3

Jastrzebska 2017

Healthy adults

No

Oral dose of 5000 IU vit D3 daily

8 weeks

280,000 IU vit D3

Dahlquist 2017

Healthy adults

No

Sport drink with 5000 IU vit D3 once

Once

5000 IU vit D3

Walentukiewicz 2018^a

Elderly women

No

Oral dose of 28,000 IU vit D3 weekly

12 weeks

336,000 IU vit D3

Panwar 2018

Adults with CKD

Yes

Oral dose of 0.5 mcg (20 IU vit D3) calcitriol daily

6 weeks

840 IU vit D3