Stopping Strontium Before Total Calcium Test

I started taking strontium citrate in 01/2008. In 2009, I had three tests for total serum calcium as part of three comprehensive metabolic panels (CMPs). On those occasions, I did NOT stop taking strontium prior to blood collection. The first two results were normal (10.1 & 9.7), but the third was slightly elevated (10.3, reference range 8.6 to 10.2 mg/dL). In 2010, I skipped my strontium dose the night before the test; my calcium was normal (9.8). In 2012, I switched labs and stopped taking strontium for 11 days prior to the test. My calcium was 10.3 but fell within the reference range (8.5 to 10.5 mg/dL) for the new lab. In 2013, I stopped strontium for 12 days before the test, and my calcium was 9.5.

Collection Date     Stopped Strontium?          Total Calcium           Ref. Range
01/06/2009                       No                               10.1                        8.6-10.2
03/19/2009                       No                                 9.7                        8.6-10.2
12/28/2009                       No                               10.3 H                    8.6-10.2
12/09/2010            Yes, night before test               9.8                       8.6-10.2
07/24/2012*          Yes, 11 days before test         10.3                     *8.5-10.5
11/12/2013            Yes, 12 days before test           9.5                      8.5-10.5 

*2012, switched labs-- Note different reference range.
All values are in mg/dL.

I have read that strontium reaches peak blood levels in 12 days of strontium intake. Servier, the manufacturer of strontium ranelate, has stated that sr. ranelate interferes with colorimetric tests for calcium. Automated total serum calcium tests are colorimetric. Urine calcium tests are usually colorimetric. If you stop taking strontium for 12 days or more, your blood level should be significantly lower than peak level. Therefore, it may be a good idea to stop taking strontium 12-14 days prior to having blood drawn for a total serum calcium and prior to collecting urine for a urine calcium test. Urine calcium values may vary considerably and are only meaningful if the patient is kept on a low-calcium, neutral-ash diet for three days before collection.

Using myself as a test subject, I do not have sufficient data to determine whether stopping strontium citrate for 12-14 days prior to a blood test significantly affects my total serum calcium levels. Stay posted. I am due for another blood test in a couple of weeks and am stopping strontium for more than 12 days before the test.