Five Common Medicines You Shouldn't Take With Coffee

Millions of people start their day with a cup of coffee, but most don't realize that caffeine can interfere with common medicines. From cold tablets to antidepressants, coffee can make some drugs less effective or cause unwanted side effects. Health experts say it's important to know which medicines don't mix well with your morning brew. A quick conversation with a doctor or pharmacist could save you weeks of problems.

Caffeine is a stimulant, which means it speeds up the brain and nervous system. Cold and flu medicines often contain a drug called pseudoephedrine, which is also a stimulant. When you take pseudoephedrine and drink coffee at the same time, the combined effects can be much stronger. This can cause jitteriness, headaches, a fast heartbeat, and trouble sleeping. Many cold medicines already have caffeine added to them, which makes these risks even greater.

ADHD medicines, like amphetamines, and asthma drugs, like theophylline, are also stimulants. Mixing them with caffeine can increase the chance of a rapid heartbeat and poor sleep. Some studies also show that caffeine combined with cold medicine can raise blood sugar and body temperature. This is especially important for people who have diabetes. It is best to check the label of any cold or flu medicine before drinking coffee.

Levothyroxine is the most common medicine used to treat an underactive thyroid. The thyroid is a small gland in your neck that controls how your body uses energy. If you drink coffee too soon after taking levothyroxine, your body may absorb up to 50 percent less of the medicine. Caffeine speeds up how fast food moves through your digestive system, which means the drug doesn't have enough time to be absorbed properly. It may also stick to the drug in the stomach, making it even harder for the body to use.

When the thyroid medicine isn't absorbed well, symptoms like tiredness, weight gain, and constipation can come back — even if you are taking the medicine correctly. Doctors recommend taking levothyroxine on an empty stomach with water and waiting 30 to 60 minutes before drinking coffee. A group of medicines for osteoporosis, a disease that weakens bones, also require the same careful timing. These medicines include alendronate and risedronate. Like levothyroxine, they need time without food or drink to be absorbed properly.

Some antidepressants, like sertraline and citalopram, belong to a group called SSRIs. Lab studies suggest caffeine can stick to these drugs in the stomach, which reduces how much the body absorbs. This could make the medicines less effective at treating depression and anxiety. Older antidepressants, called tricyclics, are processed by the liver using an enzyme that also breaks down caffeine. When both are present, the liver can get backed up, causing more side effects or keeping caffeine in your system longer than normal.

A medicine called clozapine, used to treat serious mental health conditions, is also broken down by the same liver enzyme. One study found that drinking just two to three cups of coffee could nearly double the level of clozapine in the blood. This could lead to serious problems like drowsiness, confusion, or worse. If you or someone you know takes clozapine, it is very important to talk to a doctor about coffee habits. Small changes in caffeine intake can have a big impact on how this medicine works.

Some painkillers, like aspirin and paracetamol, actually absorb faster when taken with coffee. This is because caffeine speeds up how quickly the stomach empties and makes the stomach more acidic. While this might make a painkiller work faster, it can also raise the risk of stomach irritation or bleeding. The risk goes up even more if a person is also getting caffeine from other sources, like energy drinks or soda. Doctors say to be careful, even though no serious cases have been widely reported.

Caffeine can also raise blood pressure and heart rate for three to four hours after you drink it. This can be a problem for people taking medicine to lower blood pressure or control irregular heartbeats. The caffeine may work against the medicine, reducing its intended effect. This doesn't mean people with heart problems must give up coffee entirely. However, they should pay close attention to how coffee affects their symptoms and talk to their doctor about it.

There are simple steps you can take to stay safe. Take thyroid and bone medicines with plain water on an empty stomach, and wait at least 30 minutes before having coffee. Be careful with cold, asthma, and ADHD medicines, since caffeine can make their side effects stronger. If you take antidepressants, antipsychotics, or blood pressure medicines, let your doctor know how much caffeine you have each day. Everyone's body handles caffeine differently, so paying attention to how you feel is key.