GoodRx Health

Not all blood clots are bad. When you cut yourself, your body springs into action by creating a tangle of substances that act like a plug. This protective response keeps us from losing too much blood.

But, sometimes, these clots can happen inside your blood vessels. This may be due to certain medical conditions, inactivity, or for no clear reason at all. These are the types of clots that can be dangerous. If they happen in your legs (called a deep vein thrombosis), they can cause swelling and pain. If they break off and block blood flow to important organs, like your heart and brain, they can cause serious problems - including a heart attack or stroke.

Fortunately, quick-acting medications like Lovenox (enoxaparin) are available to prevent and treat blood clots. Lovenox is an anticoagulant ("blood thinner") that you give to yourself as an injection under the skin once or twice a day. If you've been diagnosed with a blood clot, are planning to have surgery, or have limited ability to move while in the hospital, you'll likely come across it.

Lovenox, though, isn't immune to side effects.

Lovenox side effects at a glance

Several Lovenox side effects are common and mild enough to be managed at home. These include:

• Minor bleeding

• Bruising

• Diarrhea

• Abnormal liver enzymes

• Nausea

• Injection site reactions

Other side effects can be more serious. They may require your prescriber to step in to help manage them. These include:

• Major bleeding, including hemorrhage

• Fever

• Shortness of breath

• Swelling

• Confusion

• Epidural or spinal hematoma

• Low red blood cells

• Low platelets, including heparin-induced thrombocytopenia

Here, we'll dive into seven notable Lovenox side effects and how to manage them.

1. Bleeding

Accidental or excessive bleeding is the most common Lovenox side effect.

While receiving Lovenox, you'll likely only experience minor bleeding. But most clinical trials only discuss the likelihood of major bleeding or hemorrhage. This includes bleeding that requires you to go to the hospital. Lovenox causes major bleeding in less than 5% of people.

Some situations and health factors increase your risk of bleeding while receiving Lovenox. These include:

• Older age

• Medical conditions that make you more likely to bleed, such as hemophilia

• Heart infection

• Recent surgery

• Recent stroke that was caused by bleeding

• Decreased kidney function

• High blood pressure in the arteries

• Taking other medications that increase bleeding risk, including antiplatelet medications like aspirin

Managing bleeds and other effects from Lovenox

You can likely treat minor cuts or scrapes at home. But you should let your prescriber know if you notice unusual bruising, bleeding from a cut or wound that won't stop, or changes to the color of your urine or stool. Bleeding into the urine usually causes it to turn red, pink, or tea-colored. Bleeding into the gut usually causes your stool to look red or black.

You should also let your prescriber know if you fall while using Lovenox, especially if you hit your head when you fell. You can avoid falls by changing up your home environment, wearing proper fitting shoes, and avoiding medications that make you dizzy or blur your vision.

If you're feeling dizzy, short of breath, or you can't control the bleeding, you should call 911 or head to the ER right away. And if you know you have an active bleed in your body, you shouldn't use Lovenox.

Tip: You can further decrease your bleeding risk by avoiding over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) that increase bleeding risk, such as ibuprofen (Advil, Motrin). Be sure to talk with your prescriber before taking these medications with Lovenox.

2. Injection site reactions

Injection site reactions are another common Lovenox side effect. These include pain, bruising, and bleeding at the area where you inject the medication.

To lessen the chance of injection site reactions, consider the following strategies:

• Avoid injecting Lovenox into skin that has bruises or scars.

• Avoid rubbing the area after injecting Lovenox.

• Rotate the area where you inject the medication, alternating between the right and left side of your belly.

• Apply a warm compress or an ice pack for 10-20 minutes after the injection.

Injection site reactions are typically short-lived. Talk to your healthcare team if your symptoms don't improve after several days despite trying some of the methods listed above.

3. Diarrhea

Diarrhea is another relatively common Lovenox side effect. Diarrhea is typically a side effect you can treat at home. But it's ideal to stay ahead of it so you don't get dehydrated from fluid loss.

Recommended options for treating diarrhea include:

• Avoiding fatty, fibrous, or fried foods

• Rehydrating with clear fluids, such as broth, electrolyte beverages, or water

• Taking an OTC anti-diarrheal medication, such as Imodium (loperamide)

Reach out to your healthcare team if your diarrhea doesn't improve.

4. Swelling

Swelling in the extremities (legs, hands, and feet) is another possible Lovenox side effect. Importantly, swelling is a symptom that is also a possible sign of a blood clot. This may make it difficult to tell whether the swelling is caused by Lovenox or a blood clot.

It's important that you don't try to make this distinction on your own. If you experience swelling while prescribed Lovenox, it's best to contact your prescriber. They may request you come in for an examination and order an ultrasound to make sure you're OK.

5. Abnormal liver tests

Lovenox can sometimes increase liver enzymes. Liver enzymes are proteins that break down medications and perform other important jobs in the liver. Increased liver enzymes can be a sign of liver injury. Your prescriber should check your liver enzymes before and during Lovenox treatment.

In Lovenox's case, liver enzyme elevations are usually mild and temporary. You probably won't even experience any symptoms. However, it's important to understand which symptoms may come alongside serious liver issues. If you notice new stomach pain, dark urine, or bloating while receiving Lovenox, you should let your healthcare professional know without delay.

6. Epidural or spinal hematomas

An epidural or spinal hematoma is a rare but serious side effect of Lovenox. This refers to blood that pools in the space between the bone and the lining of your brain or spine. The blood can press on your nerves and cause paralysis.

Hematomas can happen as a result of receiving Lovenox while receiving numbing agents in the spine (epidural anesthesia) or undergoing procedures that collect spinal fluid (spinal puncture). Lovenox has a boxed warning for this side effect, which is the strongest medication warning the FDA can give.

There are certain scenarios that increase your risk of hematomas while receiving Lovenox. These include:

• Having a long-term tube, called a catheter, in your spine

• Taking other medications that increase bleeding, including antiplatelets, anticoagulants, and NSAIDs

• A history of multiple epidural or spinal punctures

• Previous surgery on the spine

• An unusually shaped spine

If you're receiving anesthesia in the spine or having a spinal puncture, your surgery team will educate you on when to stop Lovenox before the procedure. They'll also tell you when it's safe to restart it.

7. Low platelets and heparin-induced thrombocytopenia

Thrombocytopenia, or low platelets, is another rare Lovenox side effect. Platelets are blood cells that play an important role in clotting. When they're too low, the risk of bleeding is higher.

Low platelets during Lovenox treatment are likely related to a condition called heparin-induced thrombocytopenia (HIT). In HIT, your immune system activates platelets and causes them to clump together and appear low in number. But the clumped platelets can actually contribute to blood clots in some people. These blood clots can cut off important blood flow to your legs, arms, and other organs.

HIT usually shows up as a significant decrease in your platelets around 5 to 14 days after you start Lovenox. Your healthcare team will determine your risk for HIT and how often they plan to get a blood draw to monitor your platelets. If you do develop HIT, your healthcare team will stop your Lovenox doses and adjust your anticoagulation plan.

If you've been diagnosed with HIT in the past, you shouldn't receive Lovenox for at least 100 days after being diagnosed. You also shouldn't receive Lovenox if you have antibodies in your blood that show you've had HIT in the past.

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