What is a round pill with L24 on it? Identifying Levothyroxine vs. Lisinopril

October 10, 2025 •

4 min read

It is estimated that over 70% of medication errors and adverse drug events are preventable, highlighting the critical importance of proper pill identification. If you've found a round pill with L24 on it, its identity is not immediately clear, as the marking can be confused with two different prescription drugs depending on the color and full imprint.

Quick Summary

A round pill with 'L24' can be either a blue Levothyroxine for hypothyroidism or a white Lisinopril for high blood pressure. Accurate identification depends on the pill's color and other markings, such as an 'M' imprint, and is crucial for patient safety. Always consult a healthcare professional to confirm any medication.

Key Points

Two Possible Pills: A round pill with 'L24' can be either Levothyroxine Sodium (if blue) or Lisinopril (if white).
Levothyroxine Details: The blue, round pill with 'L 24' is for hypothyroidism and other thyroid conditions, manufactured by Lupin Pharmaceuticals.
Lisinopril Details: The white, round pill with 'M' on one side and 'L over 24' on the other is Lisinopril, an ACE inhibitor for high blood pressure and heart conditions.
Check All Features: Color is a key differentiator, and additional markings like the 'M' on the Lisinopril pill are critical for identification.
Consult a Professional: Due to the different uses and risks, including a serious black box warning for Lisinopril during pregnancy, always consult a pharmacist or doctor for confirmation.
Never Guess: Never take an unidentified pill based on assumption. Incorrect medication can lead to severe health complications or adverse effects.

Before discussing the identification of a round pill with 'L24' on it, it's important to state that this information is for general knowledge only and should not be taken as medical advice. Always consult with a healthcare provider or pharmacist before taking any medication or to identify an unknown pill.

Pill imprints are standardized codes used to identify medications, but seemingly similar marks can refer to different drugs. Correctly identifying a pill based on its imprint, shape, and color is a vital step in medication safety. For a round pill marked with "L24" or similar variations, the two most likely candidates are Levothyroxine and Lisinopril.

Is the pill blue with the imprint 'L 24'? It could be Levothyroxine Sodium.

If you have a blue, round pill with the imprint 'L 24', it has been identified as Levothyroxine Sodium. This is a thyroid medication manufactured by Lupin Pharmaceuticals, Inc.

What is Levothyroxine used for?

Levothyroxine is a thyroid drug used to treat a number of thyroid-related conditions, including:

Hypothyroidism: A condition where the thyroid gland does not produce enough thyroid hormone.
Hashimoto's disease: An autoimmune disorder that causes hypothyroidism.
After Thyroid Removal: Following surgery to remove the thyroid gland.
TSH Suppression: To suppress the production of thyroid-stimulating hormone (TSH) in patients with certain types of thyroid cancer.

Important warnings and side effects of Levothyroxine

While generally safe when taken as prescribed, Levothyroxine can have side effects. Some mild side effects may include temporary hair loss in children, or signs of hyperthyroidism (overactive thyroid) if the dose is too high. Serious side effects are rare but can occur with overdosage. It is critical to take this medication exactly as directed by your doctor, as the dose is highly individualized.

Is the pill white with the imprint 'M' and 'L over 24'? It could be Lisinopril.

If the pill is a white, round tablet with a distinct 'M' on one side and a stacked 'L over 24' on the other, it is identified as Lisinopril. Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor.

What is Lisinopril used for?

Lisinopril is primarily used to treat heart-related conditions:

High Blood Pressure (Hypertension): It helps relax blood vessels and lower blood pressure.
Heart Failure: It is used in combination with other medications to treat heart failure.
Post-Heart Attack: It is used to improve survival rates and prevent further damage after a heart attack.

Important warnings and side effects of Lisinopril

Lisinopril comes with several serious warnings and potential side effects:

Boxed Warning for Pregnancy: Lisinopril can cause harm and even death to an unborn fetus. It should not be used by women who are pregnant or may become pregnant.
Angioedema: This rare but serious side effect involves swelling of the face, throat, tongue, or extremities and can be life-threatening.
Common Side Effects: A persistent dry cough is a well-known side effect that sometimes requires switching medications. Other common effects include dizziness, fatigue, and headache.

How to safely identify your pill

Because of the potential for confusion between these two very different medications, it is critical to rely on all available information to identify a pill found unexpectedly. Never assume its identity based solely on a partial imprint or a guess.

Here are some steps for safe identification:

Examine all markings: Check for additional letters or numbers on the pill, and look at both sides.
Note the color: The color is a key distinguishing feature between Levothyroxine (blue) and Lisinopril (white).
Determine the shape: Ensure the pill is indeed round and not oval or another shape.
Use a professional resource: Cross-reference all features with a pill identifier database on a reliable website like Drugs.com or a pharmacist.
Consult a professional: The safest course of action is to speak with a pharmacist or doctor. They can provide an accurate identification and explain the medication's use.

Comparison Table: Levothyroxine vs. Lisinopril


Feature	Levothyroxine (Blue, round, 'L 24')	Lisinopril (White, round, 'M' & 'L over 24')
Drug Class	Thyroid Drug	ACE Inhibitor
Active Ingredient	Levothyroxine Sodium	Lisinopril
Primary Use	Hypothyroidism, Hashimoto's disease	High blood pressure, heart failure, post-heart attack
Manufacturer	Lupin Pharmaceuticals, Inc.	Various manufacturers (based on imprint 'M L24')
Color	Blue	White
Key Side Effects	Hyperthyroidism symptoms (if over-dosed), hair loss	Persistent dry cough, dizziness, headache, angioedema
Key Warning	Serious fetal toxicity if used during pregnancy	Black Box Warning: Fetal toxicity in pregnancy

Conclusion: Prioritize safety over guesswork

The presence of an L24 marking on a round pill is ambiguous without additional information like color and other imprints. The two most common possibilities are a blue Levothyroxine and a white Lisinopril, each used for vastly different medical conditions and with unique risks. In any situation involving an unidentified pill, it is crucial to prioritize safety by noting all characteristics and consulting a healthcare professional for accurate identification. Never take a medication that has not been prescribed to you, and always keep medications secured to prevent accidental ingestion. When in doubt, call your doctor or pharmacist. A reliable pill identifier tool can offer guidance, but it is not a substitute for professional medical advice.

Use the Drugs.com Pill Identifier to verify your findings and view images.

Frequently Asked Questions

A round, blue pill with the imprint 'L 24' is Levothyroxine and is used to treat thyroid conditions. However, you should only take it if it has been prescribed to you by a doctor. The dosage is highly specific to the individual, and self-medicating is dangerous.

A white, round pill with 'M' and 'L over 24' is Lisinopril, a medication for high blood pressure. However, you should never take a medication that was not prescribed specifically for you. Lisinopril has a black box warning for pregnancy and serious side effects, so proper dosage and medical guidance are essential.

The most serious risks include a black box warning for fetal toxicity, meaning it can cause harm to an unborn baby. It also carries a rare but serious risk of angioedema, which is severe swelling of the face, throat, or tongue.

If you find an unidentified pill, the safest action is not to take it. Secure it away from children and pets. The best course of action is to take it to a pharmacy for positive identification or dispose of it safely through a medication take-back program.

The most important distinguishing factors are the color and the full imprint. The Levothyroxine pill is blue with 'L 24'. The Lisinopril pill is white with 'M' on one side and 'L over 24' on the other.

Based on the identified medications, both Levothyroxine and Lisinopril are prescription-only drugs. Therefore, any round pill with this imprint is a prescription medication and should not be taken without a doctor's order.

Mistaking these two medications is dangerous because they treat completely different conditions. Levothyroxine affects the thyroid, while Lisinopril is for blood pressure and heart function. Taking the wrong medication could cause serious harm, including allergic reactions, severe side effects, or a dangerous drop in blood pressure.