How much water – or Stanley cup refills – should you have each day?

(NEXSTAR) – At some point, you may have heard that eight glasses of water a day (or roughly one of the largest Stanley tumblers that has inspired a national obsession) is a key to healthy living, but do experts really agree?

The answer can be confusing, especially with wildly different advice from popular TikTok accounts and other social media channels.

One TikToker suggested downing two to three gallons of water daily (preferably sparkling), while another recommended drinking half your weight in water ounces per day.

But what about the classic “eight glasses” advice?

“While it’s a good rule of thumb, this guidance does not take into consideration the individual needs of the patient,” Kristin Kirkpatrick, RD, a registered dietician with the Cleveland Clinic, told Nexstar. “Because hydration levels are dictated by multiple factors (age, activity level, weight, disease status, etc) and because hydration can be achieved in multiple methods (drinks, water rich foods, etc) this advice is really only general.”

Kirkpatrick tells her patients to think about what their day looks like – running a marathon in summer heat will require much more fluid intake than sitting behind a desk for eight hours in a climate-controlled office, for instance.

“A good rule of thumb is to monitor urine, looking for a faint yellow color as an indicator of perfect hydration,” Kirkpatrick said.

A report from the Institute of Medicine of the National Academies found that, on average, adequately hydrated women consumed 91 ounces of water per day, while men consumed 125 ounces. That number, however, includes not just sips of water but also fluids from other beverages and foods.

“We don’t offer any rule of thumb based on how many glasses of water people should drink each day because our hydration needs can be met through a variety of sources in addition to drinking water,” said Lawrence Appel, the director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins University.

Signs you should drink more water

While there may not be a one-size-fits-all hydration guideline, Kirkpatrick says there are telltale signs when someone isn’t drinking enough water.

These can include feeling tired, lightheaded, dizzy, or getting a headache.

Additional signs can include a lack of regular urination, dark-colored urine, dry mouth, sugar cravings, or hunger pangs.

So what’s the best way to stay hydrated? Kirkpatrick suggests carrying a water bottle that can act as both a hydration source and a reminder to drink.

If water just isn’t your beverage of choice, don’t forget that consuming other sources of fluids such as soup, decaffeinated coffee, lettuce, spinach and melons, for example, can also help you hydrate.

Can you drink too much water?

While drinking enough water can help with weight loss, mental clarity, temperature regulation and your overall health, it is possible to overdo it.

“There is a condition called hypernatremia – it’s rare but occurs when excessive water is consumed without the inclusion of electrolyte, so sodium levels become dangerously low,” Kirkpatrick told Nexstar. “Normal water consumption does not create this.”

Known as hyponatremia, the rising water level in the body can cause cells to swell, leading to potentially life-threatening medical conditions according to the Mayo Clinic.

Symptoms include nausea, vomiting, headache, confusion, loss of energy, restlessness, irritability, muscle weakness, spasms, cramps, seizures and coma.

The CDC recommends drinking water at shorter intervals rather than throwing back large quantities infrequently.