how much caffeine is safe to drink when trying to strengthen bones?

One study: "Investigating the effects of coffee on how the kidneys regulate calcium in the body, researchers found that high doses of caffeine (800 mg) consumed over a six-hour period almost doubled the amount of calcium lost in the urine."

Two cups (real cups, not Starbucks grande!) is around 280 mg or so. You'd have to be drinking a lot of coffee to reach 800. If you're having a cup or two, I wouldn't worry.

Observational studies are mixed on whether caffeine consumption increases bone density or reduces bone density. The only cause/effect information I've found is that caffeine can reduce calcium absorption. 99% of the caffeine you consume is out of your digestive system within 45minutes. Calcium is usually absorbed in a two hour period after consumption. Limit suggestions in the literature are 800mg and 400mg. You might just be certain to take both D and Calcium 45minutes after caffeine, or 2 hours before.
You probably already know that the biggest factor affecting women's bones is the loss of estrogen.

This post meant to say that 99% of the caffeine you consume is through your digestive tract within 45min.

I did not know there was a connection between loss of estrogen and osteoporosis. I just started a low dose of estradiol. I'm wondering if that will help
My Doc is suggesting EVENITY Tymlos, which I am currently researching. Any information and/opinions would be appreciated.

vinitajo74,
estradiol is bone protective. It reduces the cells that break bone down.
Usually by the time we realize the connection between bone loss and estrogen, we've already lost (and damaged) a lot of bone. At this juncture we need the cells that break bone down, so that we can rebuild new bone on a stable surface.
A choice between Evenity and Tymlos would depend upon your bone density measurements. Tymlos builds better bone. It remodels-- removing the older fissured bone and laying down new integrated bone.
Evenity would be a good choice if you were likely to fracture soon. It lays down dense bone on the surface of existing bone. I think of it as a temporary scaffold. It builds bone density rapidly without repair.
If your weakest bone is in your spine, you'd fare better with Forteo. If your bone density is lowest in the hip, Tymlos would be a better choice.
I also think that the anabolics Tymlos and Forteo cause side effects in fewer individuals. both drugs stay in your system for usually four hours, so if you have an unpleasant experience, you can easily stop the medication.
Back to estradiol, though, I don't think it is strong enough to either save your bones or interfere with any of the osteoporosis medication you might take. I do think it a very good idea to take it, especially the patch.
Connect is an interesting place to gather ideas. You do have to question everything anyone says, and reach you own opinion. I wait for your

questions. Welcome to Connect.