Heparin Vs. Warfarin - Anticoagulants

Heparin Vs. Warfarin - Anticoagulants

Both of these mediations are anticoagulants but they have core difference you should be aware of!

Hey there! It's Kristine from Nurse In The Making. Today I'm going to talk about anticoagulants, specifically Heparin and Warfarin! If you're following along with your pharmacology flashcards, I'm in the cardiovascular section on the Heparin and the Warfarin card.

Anticoagulant Overview

Before we dive into the core differences between these two medications, let's talk about what anticoagulants do and what they don't do.

✔️ What anticoagulants do is they prevent new clots from forming and they prevent current clots from getting bigger. 

❌ What anticoagulants don't do is thin the blood. You'll hear Heparin and Warfarin referred to as blood thinners. But don't let that confuse you. They DO NOT THIN THE BLOOD or dissolve clots, they only prevent new clots from forming or prevent current clots from getting bigger.

Therapeutic Uses

These medications prevent or treat blood clots in those with DVTs (Deep Vein Thrombosis), PEs (Pulmonary Embolisms), and A-fib, which is a dysrhythmia that causes blood to accumulate in the heart's chambers, causing blood clots. It also helps prevent clots such as DVTs and PEs postoperatively, meaning clients who just got out of really long surgeries are at increased risk for blood clots.

Medication Names

All right. Let's dive into the medication names. The brand name for Warfarin is Coumadin. Heparin is a little bit more difficult because it's available as Heparin sodium and something else called Low Molecular Weight Heparin. You'll see it written as LMWH, also called fractionated Heparin. An example of a Low Molecular Weight Heparin is enoxaparin, brand name Lovenox.

Low molecular weight Heparins are easy to recognize because of their SUFFIXES. The suffix is PARIN, like EnoxaPARIN or DaltePARIN

🧠Here's a study tip for pharmacology🧠

Learn the suffixes for each medication class rather than memorizing each medication individually. It's almost impossible to remember every single medication in your textbook. So I like to use this thing called saved by the suffixes method for learning medications.

The difference between Heparin and Low Molecular Weight Heparin is that Low Molecular Weight Heparins produce a more stable response and they have a lower chance of bleeding than Heparin sodium. 

Key Differences Between Heparin and Warfarin

Let's dive into the key differences between these two medications. Heparin can be given intravenously or subcutaneously. However, Heparin can not be given orally because Heparin is inactivated by gastric acids in the stomach. Warfarin can be given orally or intravenously, but it's most commonly given orally.  

The onset of these medications are very different. Heparin’s onset is really rapid. It can take just minutes to take effect. This is why it's great for a short term therapy. You can remember this by the 💡 memory trick: Heparin happens FAST.

The onset of Warfarin is much different. The onset is slow. It can take hours to take effect and even days to reach maximum therapeutic levels, which is why it's great for a long-term therapy. You can remember this by the 💡 memory trick: Warfarin You have to WAIT! 

Can you give Heparin and Warfarin Together?

A common question that's asked is “can you give Heparin and Warfarin together?” The answer is YES. Both medications will be given for several days until Warfarin reaches therapeutic levels. Heparin works immediately, which allows time for Warfarin to take effect.  

Are these medications safe for pregnancy?

OK, let's talk about the effects of these medications during pregnancy. Heparin is safe to give during pregnancy because it does not cross the placenta or into the breast milk. Warfarin is not safe during pregnancy because it crosses the placenta and is teratogenic, meaning it causes harm to the developing fetus.

💡 A memory trick for this is: Warfarin think WAIT, don't give that to a pregnant person. 


Now for monitoring of these medications. So many students get confused with this topic, but I'm going to break it down into simple terms. Heparin is measured with something called aPTT, and Warfarin is measured with something called INR. You can remember Heparin is measured with aPTT because Heparin has a P in it, and Warfarin does not.

aPTT stands for Activated Partial Thromboplastin Time and INR stands for International Normalized Ratio. These are coagulation tests. They are blood tests to measure how fast or slow the blood is clotting and measured in seconds.  

Here are some must-know numbers when remembering aPTT and INR. The normal range for aPTT when taking Heparin is 47 to 70 seconds. The normal range for INR while taking Warfarin is 2 to 3 seconds. 

What does it mean when these values are out of range?

If aPTT or INR is too high, there is an increased chance for bleeding. The 💡 memory trick is: Numbers are too high, patients will die, meaning from bleeding out. But if these numbers are too low, the clots will grow so this is why we want to make sure these lab values are in a therapeutic range because if they exert their effect too much, the patient can bleed out. If they aren't working enough, the clots will grow.  


Each medication has an antidote. You would give this antidote if aPTT or INR exceeds the therapeutic level or if there's evidence of bleeding. The antidote for Heparin is protamine sulfate. You can remember this by the 💡memory trick: You will need HELP from a PRO to stop bleeding out. 

The antidote for Warfarin is Vitamin K. You can remember this by the 💡memory trick: During WAR, Vitamin K kills Warfarin 

Patient Teaching

Let's talk about some patient teaching while a patient is on Warfarin, you want to educate your patient to be consistent with their Vitamin K intake. Vitamin K foods include green leafy vegetables like kale, spinach, and liver. 

Think about this: I just said the antidote for Warfarin was Vitamin K. So if the patient consumes too much Vitamin K, it's like they're consuming the antidote and it will make the medication ineffective. So tell your patients to be consistent with their vitamin K intake. Don't drastically increase or decrease their intake of Vitamin K. 

The NCLEX word here is BE CONSISTENT with their Vitamin K intake.

Some patient education for Heparin is about administration. When educating your patient about Heparin, you want to educate them to administer the medication subcutaneously in the belly two inches away from the umbilicus, meaning the belly button, at a 90 degree angle. Do not massage the site after injection and educate your patient that it's common to have bruising, irritation, and pain after administration. 

A complication of both Warfarin and Heparin is that they both cause increased risk for bleeding. So we want to teach our patients about bleeding precautions. This includes:

  • Avoiding NSAIDs, aspirin, antibiotics, & alcohol (even alcohol-based mouthwash)
  • Gently brush teeth with a soft-bristled toothbrush
  • Avoid contact sports
  • Remove throw rugs to reduce risk for falls
  • Use an electric razor
  • Wear a MedicAlert device


OK, let's review the key differences. Heparin is given IV or SubQ, It cannot be given PO. Warfarin is most commonly given PO.  

Heparin is safe to give during pregnancy while Warfarin is teratogenic and should be avoided during pregnancy.  

Heparin’s onset is rapid while Warfarin’s onset is slow.

Heparin is monitored with aPTT and Warfarin is monitored with INR. 

The antidote for Heparin is protamine sulfate and the antidote for Warfarin is Vitamin K. 

And remember, they both increase the risk for bleeding. 

That's all for Heparin versus Warfarin.  

If you want more pharmacology information like this, you can find it in the pharmacology flashcards.

Happy studying future nurses!


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