Calcium supplements are all over.  Make sure to choose a calcium supplement based on the amount of elemental calcium.  Also make sure your calcium supplement has a "USP" or "CL" on the label to ensure its purity and that it will dissolve in your stomach.

Anytime somebody hears about calcium they assume that they can just go out and buy anything and that it's all the same.

There probably isn't a week that goes by that this doesn't cause a lot of confusion for other patients and readers.  The good news?  I think I can help clear up your confusion by starting out with a simple chemistry lesson.

When you look on the shelf you likely see different forms of calcium like calcium citrate, calcium gluconate and calcium carbonate.  All are 'salt' forms of calcium.

No, I'm not talking table 'salt'.

What this means is that attached to every calcium is a 'salt' like carbonate, gluconate or citrate.

Chemically, calcium has two 'positive' charges.  So it needs a negative 'salt' to attach to it so our bodies can use it.

The problem is when you attach different salt to any kind of molecule it can change the absorption and so forth of the drug.

Even so, you can avoid all the confusion by completely ignoring the labeling on the front of the bottle and instead focus on the nutrition facts on the back of the bottle.  That is because the nutrition facts on the back of the bottle ignore whatever kind of salt form is attached and instead give you only the actual amount of elemental calcium that is contained in each serving.

For example, Tums® is a good source of calcium.  It's salt form is calcium carbonate.  Calcium carbonate is usually provides around 40% elemental calcium.

So, for every 500mg Tums® tablet you take you get 200mg of elemental calcium.  That's the number you are really concerned about.

Calcium citrate has a higher concentration of elemental calcium per serving.  But, it is more expensive to purchase.

More is Not Better

I'll encounter folks sometimes who take the 'more is better' approach to almost any supplement.  That's a bad practice, but especially bad with calcium.

Most experts recommend not going over 2500mg a day of elemental calcium.  Doing so could put you at greater risk for kidney stone formation and other kidney complications.  Also, I believe that it may put you at risk for other complications especially if you have joint problems as your body may deposit extra calcium on your joints.

For calcium the % daily value is listed as 1,000mg of elemental calcium.  There are variations of this.  For example, pregnant woman and the elderly require more.

So, before taking a calcium supplement try to guesstimate how much you are getting from your food.  Obviously, if you are eating the way I recommend you'll be getting ample amounts and may not need to supplement.  But, if you find you need to supplement here are some points to keep in mind when choosing your supplement:

Do try and find a calcium supplement that has "USP" (United States Pharmacopoeia) or "CL" (ConsumerLab) abbreviation  on it.  In layman's terms this means that particular calcium supplement has met voluntary standards for quality, purity and tablet disintegration.

In addition to that these abbreviations assure that the product contains no lead (or very low levels of lead) or other metals.  It is OK to have a little lead in there because calcium actually blocks lead absorption.

Other Points to Consider

• The abbreviations are also important because to be absorbed into your bloodstream calcium must dissolve in your stomach.  If you did happen to buy a supplement without the USP or CL label just throw a tablet in some vinegar (which is acidic and will replicate your stomach conditions).  If it dissolves in at least 1/2 hour then it's OK.  If it doesn't then you'll want to look elsewhere.
• Make sure you check for interactions with any prescription medications you might be one right now.  As a safeguard try to take your calcium supplement 2 hours before or 1 hour after any other supplement or prescription medication.  A good example are the quinolone antibiotics like Levaquin® or Cipro®.  Calcium can 'bind' to these drugs and make them less effective.
• A lot has been made about having vitamin D in whatever calcium supplement you choose to increase its absorption.  That's a bit of a marketing ploy.  Remember, vitamin D is primarily synthesized in your body from exposure to the suns UV rays.  Your body can store vitamin D to a point.  So, even if it is winter you likely still have some vitamin D so you may not need to supplement. 
  
• If you do need vitamin D I would recommend a quality cod liver oil which also contains vitamin A - which your body needs more of when accessing vitamin D.  This is one of the reasons why a healthy lifestyle is paramount.  There are so many interrelated pathways and so forth that just trying to pick off one mineral or vitamin or herb is hard to do and may even set you back farther.  If you are truly concerned about your vitamin D intake, get your blood levels tested.
• Magnesium and phosphorous are also critical elements for calcium absorption.  And, while they might be touted as being contained in your particular calcium supplement I'd caution you from getting too carried away thinking you need them until you establish your bodies actual blood levels of these compounds.

As with vitamin D above, you may be supplementing with something that you frankly don't need.