Your body obtains vitamin D from sunlight, as well as from particular foods, such as dairy products and fatty fish. Once it is present in the body, vitamin D then needs undergo a precise activation pathway before it can actually be used by the body to support bone health and immune function.

When UVB rays from the sun hit your skin, they convert 7-dehydrocholesterol into vitamin D₃ (cholecalciferol), which is the starting form of vitamin D. This form then travels to your liver, where it becomes calcifediol (25-hydroxyvitamin D or 25(OH)D). This is the main circulating form that is used to measure your vitamin D levels in blood tests and is therefore the key marker of your vitamin D status. From there, calcifediol moves to your kidneys, where it is converted into calcitriol (1,25-dihydroxyvitamin D), which is the active hormone responsible for regulating calcium and phosphate balance, and supporting bone and muscle function.

Most vitamin D supplements contain cholecalciferol, which still requires conversion in your liver before it can raise blood levels. However, calcifediol monohydrate is already in the 25-hydroxyvitamin D form, meaning it bypasses that first conversion step and can directly contribute to the circulating vitamin D levels used in blood testing. Calcifediol monohydrate can therefore increase vitamin D status more rapidly and predictably than standard vitamin D₃, especially where absorption or conversion is impaired.

Now a new generation of vitamin D supplements has arrived with Ampli-D®, a clinically studied form of calcifediol. According to manufacturer data from DSM-Firmenich, Ampli-D® can raise vitamin D levels up to three times faster and more effectively than conventional vitamin D₃ supplementation, achieving improvements in days rather than months. Calcifediol is already the circulating form of vitamin D, so it is highly bioavailable; nor does it rely on the same liver conversion step that cholecalciferol does. Calcifediol monohydrate, including newer formulations like Ampli-D®, therefore sit closer to the body’s own circulating vitamin D pool, making it a faster, more targeted and modern way to restore and support vitamin D levels, especially in people who need quicker correction or have difficulty maintaining adequate status.

References available on request.

Vitamin D is essential for calcium absorption in the gut, maintaining normal blood calcium levels, immune system health and bone strength and structure. Healthy Bones Australia advises adequate levels of vitamin D are essential for long-term skeletal health. However, even in sunny Australia, deficiency is surprisingly common. Higher-risk groups include people:

Pregnant and breastfeeding women and older adults, especially those in residential care, are also consistently identified as being at risk.