What Causes Sudden Memory Loss?

Medically Reviewed by Christopher Melinosky, MD on October 12, 2023
Written by WebMD Editorial Contributors
5 min read

It's normal to forget a word, misplace your keys, or have trouble remembering directions once in a while. These kinds of memory slips become more common as you get older. Yet sudden and severe memory loss – such as forgetting your children's names or not knowing where you are -- can signal a more serious problem.

Memory loss can be a sign of Alzheimer's disease and other types of dementia. But when it comes on quickly, it's often because of other things. Many of these causes are treatable.

Here are some things that can lead to sudden memory loss -- and what you can do about them:

Many prescription drugs you might take can affect your memory. This is not a full listing, but some of the most common ones include:

If you take one of these drugs -- or even something not on this list -- and are worried about your memory, ask your doctor if you can switch to something else.

Your memory and emotions are closely connected. Depression, stress, or anxiety can affect your focus. When you can't focus, you can't remember very well.

If you feel sad or have lost interest in things you once enjoyed, see a mental health professional to get treated. Antidepressants and talk therapy can help with depression.

Too little vitamin B12 in your diet can also affect your memory. This nutrient helps your body use energy from food, and it protects nerve cells so you can think clearly.

Your body doesn't make vitamin B12. You get it from foods such as meat, fish, milk, cheese, and eggs. Some vegans might not get enough vitamin B12 from diet alone. If you're low in this vitamin, ask your doctor about taking a supplement.

In large amounts, alcohol makes it harder to form new memories or store information you've learned.

If you binge drink -- have many drinks in a short time -- you may sometimes “black out.” You can forget entire chunks of time. If you keep drinking too much, memory loss can become permanent.

A fall, car accident, or other hard knock to the head can leave you unable to remember people or events. Even if the injury doesn't knock you unconscious, it can lead to memory loss.

Depending on how severe the hit to your head was, the memory issues might go away or be permanent.

A stroke happens when a blockage or weak area in a blood vessel cuts off blood flow to part of your brain. Without oxygen-rich blood, brain cells start to die. A stroke can cause short-term or long-term memory loss. You might forget things you've learned or get easily confused.

To protect your blood vessels and prevent more strokes:

Amnesia is when you suddenly can't remember things about yourself or your life. It can be caused by injury or damage to your brain.

“Transient global amnesia” is a type of memory loss where you suddenly forget where you are or what's happened recently. You might ask the same questions over and over to get your bearings.

This type of amnesia is usually spontaneous and can happen after:

Transient global amnesia is rare and doesn't need to be treated. It should get better on its own.

Damage to the brain from a tumor or its treatments can affect memory. Chemotherapy, surgery, and radiation can affect your ability to think clearly. Cancer can also make you so tired that you can't think straight.

Take care of yourself while you're being treated for cancer. Eat well and get plenty of rest to save energy and keep your memory.

The thyroid gland in your neck produces hormones that control how quickly your body burns food for energy. When your thyroid makes too little of its hormones -- called hypothyroidism -- your whole body slows down. You can feel tired, depressed, and forgetful.

Your doctor will do a blood test to check your thyroid hormone levels. If they're low, you'll get thyroid hormone pills.

If you're worried about memory loss, see your doctor. They will ask questions about your symptoms and do tests to find out what's behind the problem. Many causes of memory loss can be treated.