Although we want to think that osteoporosis medications increase our bone density, it's very common for the bone density tests to stay the same on bisphosphonates such as Fosamax.
On an anabolic agent, like teriparatide (Forteo), bone density should almost always increase unless there is an underlying medical condition causing the bone loss (secondary osteoporosis).
For people on medicine for osteoporosis, the most common cause of continued bone loss is vitamin D deficiency. In children, vitamin D deficiency is called rickets, but it is called osteomalacia in adults. Unfortunately, if you have vitamin D deficiency, taking the 1000 IU vitamin D is not enough to overcome the deficiency in a timely manner.
For example, patients in our clinic with ricketts will get a 50,000 IU dose for 30 days and recheck the blood level. However, it's important to check the level before and during treatment. The National Osteoporosis Foundation recently increased their recommended daily intake of Vitamin D to 800-1000 IU for patients 50 and over. That includes all sources, so if you have vitamin D intake from foods such as milk and cheese, these count towards the total.
It's important to note that that is the recommended total amount needed to prevent deficiency in healthy adults. If you already have deficiency, you will need a higher dose.
Make sure that your physician checks your vitamin D level before you are started on any kind of osteoporosis medication. If you don't have adequate vitamin D, your body can make enough new bone to overcome osteoporosis. Although many labs use 30ng/mL as the lower limit of normal for a vitamin D level, it really should be 40 or more.
About 90 percent of the patients we see (most who have fractures) have osteomalacia (rickets in adults). Also, if you have continued decrease on your Dexa despite religiously taking your medications, you should have a comprehensive metabolic workup for secondary causes--that is, something else is usually going on and several blood and urine tests are usually needed to find out why.
Always consult your physician. I recommend finding a qualified physician in your area who has an interest in osteoporosis. Preferably they will be involved with the NOF or at least aware of its recommendations. You need the best team on your side to beat this disease.