Both the Combination of Micronutrients for Bone (COMB) study and Melatonin-Micronutrients Osteopenia Treatment Study (MOTS) investigated using strontium in conjunction with other supplements. You cannot take strontium without taking sufficient calcium (from food and/or supplements) and vitamin D. You also need magnesium, which was not included in the MOTS protocol, and was provided at a very low dosage in the COMB study.
The COMB study for osteoporosis:
strontium citrate (680 mg)
D3 (2000 IU)
dietary sources of calcium
magnesium (25 mg)
K2 (MK7) (100 mcg)
DHA (250 mg)
daily impact exercises were encouraged.
MOTS for osteopenia:
strontium citrate (450 mg)
D3 (2000 IU)
K2 (MK7) (60 mcg)
melatonin, 5 mg
These ingredients were called MSDK for melatonin, strontium citrate, vitamins D3 and K2.
In addition to study medication, participants were allowed to take less than 1000 IU D3 and less than 1000 mg of calcium. Nearly 87% of the subjects in the MOTS study were taking either calcium/vitamin D3, multivitamins, and/or other dietary supplements.
The BoneLady uses her own protocol for osteoporosis:
strontium citrate (682 mg),
D3 (1300 IU)
calcium (500 mg tablet, about 700 mg from dietary sources)
magnesium (450 mg)
daily low-impact exercises
I do not take DHA, K2, or melatonin. I do take several other supplements: https://strontiumforbones.blogspot.com/2020/07/my-current-supplements.html