Calcium & dialysis: the basics
What does calcium do in my body?
Calcium, like phosphate, is an important electrolyte that your body needs to build your bones. The levels of calcium and phosphate are controlled by very complex mechanisms. Very simplified, this happens via the parathyroid gland and vitamin D.
There are about 1-2 kg of calcium stored in a human body, most of which is in your bones. Your body either puts excess calcium into your bones for storage, or it excretes it. Both too much calcium and too little calcium are not good for a person.
How does my body get calcium?
Your body absorbs calcium from the food you eat via the intestine. Dairy products in particular (yoghurt, cheese, cow's milk), but also berries, herbs, nuts and green vegetables such as broccoli or spinach leaves are relatively calcium-rich foods.
Calcium deficiency - what is it?
Unlike the well-known electrolytes potassium and phosphate, dialysis can often leave your blood rather low in calcium. Your dialysis team sometimes refers to this as hypocalcemia. Your doctor and you should definitely do something together against a calcium deficiency, because otherwise it can lead to health problems in the long run.
Is it possible to also have too much calcium?
If there is an excess of calcium, your doctor will call it hypercalcemia. Among other things, this can lead to bones becoming more brittle. This is called decalcification of the bone and a deposit of calcium in your blood vessels and tissues. A slight excess of calcium in your blood often does not cause any symptoms. However, a more severe elevation can cause fatigue, headaches, and muscle aches. Cardiovascular problems can also result from this, as the calcium in your blood vessels impedes steady blood flow.
How much calcium do I need as a dialysis patient?
As a dialysis patient, you are advised to keep your calcium blood level within the approximate target range of 2.15 - 2.5 mmol/l, just as a person without kidney disease would.
How can I influence my calcium level as a dialysis patient?
If you have a calcium deficiency, your doctor will pay close attention to this during renal replacement therapy and, if necessary, supply additional calcium via the dialysis machine.
Of course, you should also make sure that you're getting the right amount of calcium in your diet. So if you were to have a calcium surplus temporarily, you should reduce cheese a bit, for example.
What's the deal with phosphate binders and calcium?
Some phosphate binders contain a high dose of calcium. The calcium is partly absorbed by the intestines, but only parts of it can be excreted due to insufficient kidney function. Your nephrologist will usually prescribe calcium-containing phosphate binders if you are prone to calcium deficiency.
One more thing…
In your blood, calcium often connects with the protein albumin. That's why you always have to look at the combination of the two parameters. Don't worry though, that's a bit beyond the scope of what you need to know. Your doctor should take care of that.
Dialysis can result in both calcium deficiency and calcium excess
Your calcium level can be controlled by your doctor through the dialysis treatment, as well as by you through optimizing your diet
Phosphate binders that contain calcium help manage phosphate levels and may simultaneously help balancing out a too low calcium level.
- Peacock M. Calcium metabolism in health and disease. Clin J Am Soc Nephrol. 2010 Jan;5 Suppl 1:S23-30. doi: 10.2215/CJN.05910809. PMID: 20089499.
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD Update Work Group. KDIGO 2017 Clinical Practice Guideline Update for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). Kidney Int Suppl (2011). 2017 Jul;7(1):1-59.
- Ikizler TA, Burrowes JD, Byham-Gray LD, Campbell KL, Carrero JJ, Chan W, Fouque D, Friedman AN, Ghaddar S, Goldstein-Fuchs DJ, Kaysen GA, Kopple JD, Teta D, Yee-Moon Wang A, Cuppari L. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update. Am J Kidney Dis. 2020 Sep;76(3 Suppl 1):S1-S107.