Some common side effects of this drug include: Nausea, Vomiting, Unusual tiredness Keep in mind that your doctor has prescribed you this medication because its benefits to you are greater than the risk of side effects. Many people who use this medication do not have serious side effects. However, Cinacalcet can lead to low calcium in the blood, so if you undergo any serious side effects as mentioned below then notify your doctor immediately. Severe muscle spasms, Numbing of skin, Tingling of skin, Seizures, Unusual tiredness A serious allergic reaction to this drug is very rare, however, if you start seeing any symptoms of an allergic reaction such as trouble breathing, rash or swelling; visit your doctor immediately.