This specific vitamin D is in liquid form, with the only ingredients being cholecalciferol in MCT oil (medium chain triglycerides, oil extracted from coconut oil and palm kernel oil), which is why I chose it as most others I looked at have additional additives and excipients that are not only unnecessary but can also cause problems.

Because it is oil-based, it takes a while to dry, so personally, I prefer not to apply it on the skin, but it is possible. I mention this because MCT oil can cause stomach irritation in some people, although with this specific product being so concentrated (1000 IU/drop), the amount of oil you consume in one dose (a few drops) is minimal.

Personally, I take 6-7 drops per day after a meal, under the tongue. It should be noted that it does not come with a dropper, so sublingual application is a bit inconvenient, but it doesn't bother me much.

The only negative is that the cap does not seal well, and when I opened it, a small amount of liquid had leaked onto the top of the bottle. It needs to be kept upright, otherwise it starts to slowly leak. This is quite common with this specific product and other Now products that are in liquid form, and many people on Amazon have reported the same.

tldr: Quality vitamin D from a well-known and reliable company, without unnecessary additives and high concentration. 5 drops per day is enough for about 5-6 months. I will retest my vitamin D levels after about 6 months.