Rarely, too much metformin can build up in the body and cause a serious (sometimes fatal) condition called lactic acidosis. Lactic acidosis is more likely if you are an older adult, if you have kidney or liver disease, dehydration, heart failure, heavy alcohol use, if you have surgery, if you have X-ray or scanning procedures that use iodinated contrast, or if you are using certain drugs. For some conditions, your doctor may tell you to stop taking this medication for a short time. Ask your doctor or pharmacist for more details. Stop taking this medication and get medical help right away if you have any symptoms of lactic acidosis, such as unusual tiredness, dizziness, severe drowsiness, chills, blue/cold skin, muscle pain, fast/difficult breathing, slow/irregular heartbeat, or stomach pain with nausea/vomiting/diarrhea.

Nausea, vomiting, stomach upset, diarrhea, bloating/gas, headache, or weakness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. If stomach symptoms return later (after taking the same dose for several days or weeks), tell your doctor right away. Stomach symptoms that occur after the first days of your treatment may be signs of lactic acidosis. Tell your doctor if you see undissolved tablets in your stool. Your doctor may check lab tests to make sure the medication is working. Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if you have any serious side effects, including: signs of a urinary tract infection (such as burning/painful/frequent/urgent urination, pink/bloody urine), signs of kidney problems (such as change in the amount of urine), joint pain, unusual skin blisters, signs of heart failure (such as shortness of breath, swelling ankles/feet, unusual/sudden weight gain). Get medical help right away if you have any very serious side effects, including: signs of disease of the pancreas (such as nausea/vomiting that doesn't stop, severe stomach/abdominal pain which may spread to the back). This medication may cause a new yeast infection in the vagina or the penis. It may also cause a rare but very serious bacterial infection in the genital/anal area (Fournier's gangrene). Tell your doctor right away if you have signs of a yeast infection in the vagina (such as unusual vaginal discharge/burning/itching/odor) or in the penis (such as redness/itching/swelling of the penis, unusual discharge from the penis). However, get medical help right away if you have any pain/redness/swelling in or around the genital/anal area, along with a fever or feeling unwell. This medication may increase the risk of lower limb amputation (especially of the toe and foot). The risk is higher if you have poor blood flow in the legs, nerve problems, foot ulcers, or have had a previous amputation. To lessen the risk, check your feet regularly and tell your doctor if you have new pain, tenderness, sores, or ulcers on your legs or feet. This medication does not usually cause low blood sugar (hypoglycemia). Low blood sugar may occur if this drug is prescribed with other diabetes medications, or if you do not consume enough calories from food, or if you do unusually heavy exercise. Symptoms of low blood sugar include sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. It is a good habit to carry glucose tablets or gel to treat low blood sugar. If you don't have these reliable forms of glucose, rapidly raise your blood sugar by eating a quick source of sugar such as table sugar, honey, or candy, or drink fruit juice or non-diet soda. Tell your doctor right away about the reaction and the use of this product. To help prevent low blood sugar, eat meals on a regular schedule, and do not skip meals. Check with your doctor or pharmacist to find out what you should do if you miss a meal. Symptoms of high blood sugar (hyperglycemia) include increased thirst/urination. If these symptoms occur, tell your doctor right away. Your doctor may need to adjust your diabetes medication, exercise program, or diet. This medication may cause you to become dehydrated. This can lead to serious kidney damage. Drink plenty of fluids to prevent dehydration. Tell your doctor or pharmacist right away if you are not able to drink fluids as usual, or losing fluid (such as due to vomiting, diarrhea, or heavy sweating). Also, tell your doctor right away if you have any signs of dehydration, such as urinating less than usual, unusual dry mouth/thirst, fast heartbeat, or dizziness/lightheadedness/fainting. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Other medications can affect the removal of linagliptin from your body, which may affect how linagliptin works. One example is rifampin, among others. Beta blocker medications (such as metoprolol, propranolol, glaucoma eye drops such as timolol) may prevent the fast/pounding heartbeat you would usually feel when your blood sugar falls too low (hypoglycemia). Other symptoms of low blood sugar, such as dizziness, hunger, or sweating, are not affected by these drugs. Many drugs can affect your blood sugar, making it harder to control. Before you start, stop, or change any medication, talk with your doctor or pharmacist about how the medication may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of high or low blood sugar. Your doctor may need to adjust your diabetes medication, exercise program, or diet. Your urine will test positive for glucose. Make sure lab personnel and all your doctors know you use this drug.