Tips for Taking an Accurate Temperature with a Digital Thermometer

When you’re feeling off maybe a bit flushed, shivery, or just not quite yourself checking your temperature is one of the fastest ways to see if your body is fighting something. While many of us have digital thermometers on hand, getting a reliable reading isn’t always as simple as clicking it on and waiting for the beep.

Used correctly, digital thermometers are quick, accessible tools that can help determine if you're running a fever. But depending on where you measure mouth, armpit, or rectum the accuracy can vary slightly, and knowing how to use each method properly makes all the difference.

Here’s how to get a precise temperature reading, no matter which method you choose.

First, Handle With Care

Before you even take your temperature, cleanliness is key. Wash your hands thoroughly, and always disinfect the thermometer with an alcohol swab both before and after each use. If you're using a rectal thermometer for a baby or toddler, never use that same thermometer orally or under the arm. It's best to designate one thermometer per method to avoid cross-contamination.

Also worth knowing: what qualifies as a fever depends slightly on where you measure. According to the Mayo Clinic, a temperature of 100°F or higher generally indicates a fever, but rectal and ear readings tend to run higher, while armpit readings often come in lower.

How to Take an Oral Temperature

This is the most common method for adults and older children who can hold a thermometer under their tongue without difficulty.

1. Clean the thermometer with alcohol and turn it on.

2. Place the tip under the tongue, toward the back of the mouth.

3. Close the lips and keep them sealed until the thermometer beeps.

4. Remove the thermometer and read the result.

5. Disinfect and store the thermometer. Don’t forget to wash your hands again.

Pro tip: Avoid eating, drinking, or chewing gum for at least 15 minutes before taking your temperature orally these can affect the reading.

How to Take an Axillary (Armpit) Temperature

While slightly less accurate than oral or rectal readings, axillary temps can be useful for quick checks or when oral measurement isn’t practical.

1. Clean the thermometer with alcohol and turn it on.

2. Dry the armpit with a clean towel.

3. Place the thermometer under the armpit, directly against the skin (not clothing).

4. Lower the arm to hold the thermometer in place.

5. Wait for the beep, then check the screen.

6. Disinfect and store the thermometer, and wash your hands.

Note: Because this method may read lower, a fever here might be defined as 99°F or higher.

How to Take a Rectal Temperature (for Babies and Small Children)

This method provides the most accurate core body temperature and is often recommended for infants under 3 months.

1. Clean the thermometer and apply a small amount of petroleum jelly to the tip.

2. Turn the thermometer on.

3. Gently lay your child on their back, lifting the thighs up.

4. Insert the thermometer no more than ½ to 1 inch into the rectum.

5. Hold gently until it beeps.

6. Carefully remove the thermometer and read the result.

7. Clean, sanitize, and store the thermometer. Wash your hands thoroughly.

What to Do If You Have a Fever

If your thermometer reading shows a fever, it's your body’s way of saying it needs rest. According to the CDC and Mayo Clinic, here’s how to manage it at home:

• Get plenty of rest

• Stay hydrated with water, broth, or electrolyte drinks

• Take over-the-counter fever reducers like acetaminophen or ibuprofen, if recommended

• Avoid close contact with others to prevent spreading infection

Seek immediate medical care if your fever is accompanied by serious symptoms like shortness of breath, chest pain, confusion, severe headache, or abdominal pain.

Checking your temperature might seem like a small step, but it’s one of the simplest ways to take charge of your health and with a digital thermometer, accuracy is within easy reach when you follow the right steps.

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