You have temporary vision problems
Caffeine has been known to increase pressure in the eyes for a short period of time. Coffee in moderation is fine, according to the Glaucoma Research Foundation. But it is probably a good idea not to overdrink it, especially if you’re at high risk of glaucoma. Some research suggests that drinking five or more cups of caffeinated coffee a day may increase the risk of developing glaucoma, the organization notes. Additionally, caffeine may cause a spike in blood sugar levels, which may translate to blurred vision.
Your blood pressure is high
Caffeine can cause a temporary spike in blood pressure, and medical professionals are not sure why. One theory is that it blocks the production of a hormone that plays a role in the widening of the arteries. Another hypothesis has to do with caffeine’s effects on the adrenal glands. These glands release adrenaline, a hormone that causes a rise in blood pressure.
You have stained teeth
Drinking large amounts of coffee every day can lead to discolored, yellow, or stained teeth. It is so common, the side effect even has a name — coffee stains. Coffee — as well as tea and soda — gets trapped in the microscopic ridges of the enamel, the outer protective layer of the tooth, forming stains.
You’re very tired when you don’t drink coffee
Most people drink coffee as a pick-me-up drink. Chronic and excessive caffeine intake, however, may deplete energy levels after the drink’s effects wears off, according to a study of the effects of energy drinks, in which the major stimulant ingredient is caffeine. Researchers found excessive daytime sleepiness to be common the day after energy drink consumption. Caffeine triggers the sympathetic nervous system (fight or flight response), which is OK in the short-term. When it is activated repeatedly over a time, the body gets no chance to rest, leading to fatigue.
You start to hear things
Five cups of coffee a day or more in people who also feel high levels of stress may cause them to hear things, according to a study conducted by Melbourne’s La Trobe University. The study was initially researching why people who were never diagnosed with schizophrenia were showing symptoms of the condition.