Answer
The combination already supplies calcium; excessive additional calcium can increase the risk of hypercalcaemia and milk-alkali syndrome.
Sources for this answer
- Rennie Spearmint — Current selected SmPCemc · Summary of Product Characteristics
- Rennie Sugar Free — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.