What an INR Level of 3.8 means

What happens when your blood is "too thin"

Having blood that is "too thin" means you are at a greater risk of internal bleeding. You should report any falls or accidents, as well as signs or symptoms of bleeding or unusual bruising to your healthcare provider.

The most serious internal bleeding can happen in your stomach or head.

Serious Internal Bleeding Symptoms

  • An unusual or severe headache may signal intracerebral bleeding (bleeding in the head)
  • A severe stomach ache may signal gastrointestinal bleeding (bleeding in the stomach)

Excessive bleeding can occur in any area of the body.

Other Internal Bleeding Symptoms

  • Prolonged bleeding after minor cuts
  • Prolonged menstrual bleeding
  • a nosebleed
  • vomiting blood
  • bleeding from the gums
  • Blood in urine
  • Bloody or dark stool

Treatment for an INR of 3.8

Since your international normalized ratio (INR) is outside your therapeutic range, your doctor may opt to adjust your current Warfarin therapy plan.

DO NOT attempt to self-medicate. ALWAYS consult your doctor and follow his/her treatment plan.

These are some scenarios you may experience:

Stopping Lovenox Coverage

If your doctor prescribed Lovenox, then he/she will want to stop the Lovenox to avoid your blood from getting "too thin". He/she will want to recheck your INR in 4 to 7 days.6 This is because your INR of 3.8 is above your target INR range.

Lovenox is a Low Molecular Weight Heparin Blood Thinner. Low Molecular Weight Heparin or LMWH is more convenient and has fewer side effects than standard Heparin and requires fewer shots. Lovenox is injected into the abdomen and is approved for the treatment of a DVT or Pulmonary Embolisms.

Your Doctor May Do Nothing...

No dosage adjustment may be necessary if your last two INRs were in range and the reason for your HIGH INR can be pinpointed to a factor like acute alcohol ingestion or a decrease in your normal vitamin k intake. The doctor should only follow through with making no changes if he/she doesn't think there's a risk for internal bleeding.10

Pausing Your Warfarin Therapy Temporarily

The doctor may want you to hold your next Warfarin dosage to decrease your INR.10

Decreasing Your Normal Dosage

If there isn't a clear explanation for your INR of 3.8 to be out of your target INR range, then your doctor would decrease your Warfarin maintenance dose by 5%–15%. The doctor will want to recheck your INR in 4 to 7 days.6, 10

If You're Experiencing Life-threatening Bleeding

Your doctor will give you a prothrombin complex concentrate and 10 mg of vitamin K1 by infusion. Your doctor may repeat if needed. This treatment is to stop the bleeding.

A prothrombin complex concentrate is a combination of blood clotting factors prepared from fresh-frozen human blood plasma. It's used to reverse the effects of Warfarin when bleeding occurs (e.g. in the brain or gut) requiring rapid action to accelerate coagulation (speed up clotting).1

How long an INR of 3.8 will last

Warfarin stays in the body for a long time. Every 20 to 60 hours, half the Warfarin in your body will be gone (metabolized).8 A single dose of Warfarin can last two to five days in your body. 7

If your Warfarin dosage was recently changed, the change in dosage may not make a notable difference in your INR for around 72 to 96 hours (three to four days). 9

When you should have another INR test

Since your INR of 3.8 is out of the target range you should test frequently until your INR Level is in its target range. This could be every 4 to 7 days.2

These are some additional reasons you may need to test your INR more frequently:

When You First Begin Warfarin Therapy

When you're starting out with Warfarin, you should be monitored by your doctor 4-5 times a week until there's consistency with your INR test results.

Changes To Your Medications or Condition

When there are changes to medications you're taking or your medical condition You need to test more frequently because drugs and dietary changes can significantly interact with your Warfarin therapy.

When You Use Warfarin and Heparin at the Same time

When you are using Warfarin and Heparin You need to test more frequently and closely monitor your INR Level because the effect of heparin on your INR Level can lead to over-estimation of the therapeutic level of your Warfarin therapy.

Reasons your INR can fluctuate

Your INR of 3.8 is higher than your target INR range, and the following interactions could be reasons for that.

Vitamin K and your INR

If your diet changed and you took less vitamin k than you normally do, then your INR will have gone up.

It is important to have Vitamin K in your diet. The USDA recommends 90 mcg of Vitamin K every day. However, Vitamin K impacts your INR. So you should aim to have the same amount each day.

Not having any vitamin k in your diet is bad advice, because then if you falter in your diet and have some vitamin k, your Warfarin therapy would interact with the sudden increase in vitamin k. Also, vitamin k is an important vitamin.

Supplements That Increase your INR13

Supplement Recommendations/Comments
Dong Quai Coumarin derivative
Kava Kava
Red Yeast Rice
Vitamin E 

Drugs That Increase Your INR11

Drug Brand Name
Aprepitant Emend©
Armodafinil Nuvigil©
Bosentan Tracleer©
Carbamazepine Carbatrol©, Epitol©, Equetro©, Tegretol©, Tegretol©– XR, Teril©
Cigarette Smoking
Efavirenz Atripla©, Sustiva©
Etravirine Intelence©
Modafinil Provigil©
Montelukast Singulair©
Nafcillin Nallpen© In Plastic Container
Omeprazole Nexium©, Prilosec©, Prilosec© OTC, Zegerid©, Zegerid© OTC
Phenobarbital Donnatal©
Phenytoin Dilantin©, Phenytek©
Pioglitazone Actoplus© Met, Actoplus© Met XR, Actos©, Duetact©, Oseni©
Prednisone Rayos©
Rifampin Rifadin©, Rifamate©, Rifater©, Rimactane©
Rufinamide Banzel©

Alcohol And Your INR

Binge drinking alcohol will bring your INR up. Drinking 1-2 drinks will bring your INR down.13

Cranberry Juice and Grapefruit Juice

UC San Diego Anticoagulation Clinic recommends, in general, an interaction between warfarin and cranberry products is NOT expected. What they advise, as with everything, is moderation - have a glass, not a gallon of cranberry juice.

The same goes for grapefruit juice.13

Supplements / Foods

The following can increase the risk of bleeding because of their antiplatelet effect.13

  • Feverfew
  • Fish Oil/Omega 3 Fatty Acids
  • Garlic
  • Ginger
  • Ginkgo
  • Turmeric/Curcumin

Drugs That Increase the Risk of Bleeding11

Drug Brand Name(s) Type of Drug
celecoxib Celebrex© Nonsteroidal Anti-inflammatory Agents
diclofenac Arthrotec©, Cambia©, Cataflam©, Voltaren©-XR, Zipsor© Nonsteroidal Anti-inflammatory Agents
diflunisal Nonsteroidal Anti-inflammatory Agents
fenoprofen Nalfon© Nonsteroidal Anti-inflammatory Agents
ibuprofen Advil©, Midol© Liquid Gels, Motrin©, Profen©, Tab-Profen© Nonsteroidal Anti-inflammatory Agents
indomethacin Indocin© Nonsteroidal Anti-inflammatory Agents
ketoprofen Nexcede© Nonsteroidal Anti-inflammatory Agents
ketorolac Sprix© Nonsteroidal Anti-inflammatory Agents
mefenamic acid Ponstel©, Treximet©, Vimovo© Nonsteroidal Anti-inflammatory Agents
naproxen Aleve©, Anaprox©, Anaprox© DS, EC-Naprosyn©, Naprelan©, Naprosyn© Nonsteroidal Anti-inflammatory Agents
oxaprozin Daypro© Nonsteroidal Anti-inflammatory Agents
piroxicam Feldene© Nonsteroidal Anti-inflammatory Agents
sulindac Clinoril© Nonsteroidal Anti-inflammatory Agents
argatroban Acova© Anticoagulants
dabigatran Pradaxa© Anticoagulants
bivalirudin Angiomax© Anticoagulants
desirudin Iprivask© Anticoagulants
heparin sodium Anticoagulants
lepirudin Refludan© Anticoagulants
aspirin Antiplatelet Agents
cilostazol Pletal© Antiplatelet Agents
clopidogrel Plavix© Antiplatelet Agents
dipyridamole Aggrenox©, Persantine© Antiplatelet Agents
prasugrel Effient© Antiplatelet Agents
ticlopidine Antiplatelet Agents
citalopram Celexa© Serotonin Reuptake Inhibitors
desvenlafaxine Pristiq© Serotonin Reuptake Inhibitors
duloxetine Cymbalta© Serotonin Reuptake Inhibitors
escitalopram Lexapro© Serotonin Reuptake Inhibitors
fluoxetine Prozac©, Prozac© Weekly, Sarafem©, Symbyax© Serotonin Reuptake Inhibitors
fluvoxamine Luvox©, Luvox© XR Serotonin Reuptake Inhibitors
milnacipran Savella© Serotonin Reuptake Inhibitors
paroxetine Paxil©, Paxil© CR, Pexeva© Serotonin Reuptake Inhibitors
sertraline Zoloft© Serotonin Reuptake Inhibitors
venlafaxine Effexor© XR Serotonin Reuptake Inhibitors
vilazodone Viibryd© Serotonin Reuptake Inhibitors

What a target INR range of 2 to 3 means

Your INR target range is between of 2.0 to 3.0, which is preferred for people with the following conditions:1

  • Treatment for deep vein thrombosis (DVT) - blood clot in leg
  • Treatment for pulmonary embolism (PE) - blood clot in lung
  • Prophylaxis of venous thrombosis (high-risk surgery)
  • Tissue heart valves
  • Acute Heart Attack
  • Valvular heart disease
  • Atrial fibrillation

When You Are in Your Target INR Range

It is safer when you are in your target INR range, because the risks of an INR lower than your target range could indicate potential clots and an INR higher than your target range could indicate potential bleeding events.

Staying inside your target INR range of 2 to 3

Your INR of 3.8 is out of your target range. Due to Warfarin's unpredictable pharmacokinetics, studies have found that patients only spend about 60% of time within the therapeutic range.5

Since your INR Level is out of its target range your doctor will likely make dosage adjustments. However, make sure your doctor is taking into account the 4 D's! 3

Tell Your Doctor About Your 4 D's

These factors may be the reason your INR being out of its target range:

  • Diet - any major changes (fasting, weight watchers), liver or 7 consumption?
  • Drugs - any new medicines, discontinued medicines since last INR check?
  • Dose - confirm current Warfarin dose, any missed doses?
  • Disease - any recent illness, fever, N/V/D, significant pain or stress?
Track all these things that affect your INR by signing up for a FREE account here on INR Tracker. Learn More or .

Antibiotics/Antifungals and High INR Levels

Whether you are taking a topical antibiotic or one in pill form, antibiotics can suddenly elevate your INR.11, 12

"A patient could be stable at 2.5, and with an antibiotic, jump to 5. At this level, the risk of gastrointestinal bleeding increases, and a bump on the head could become a bleed in the brain," says Dr. Tejal Gandhi, associate professor of medicine at Harvard Medical School and an expert on outpatient drug safety.

It is important to regularly have an INR test when you are taking an antibiotic/antifungal with Warfarin because the effect of an antibiotic/antifungal on any individual cannot be predicted. Your doctor may reduce your dosage if he/she sees a spike in INR due to the antibiotic.

"It is most important to monitor Warfarin patients as soon as they start a new antibiotic. If we see a small rise in INR with a two to three-day course of prophylactic antibiotics before dental work, we may not worry, because the antibiotic leaves the system quickly. However, if we see an upward rise in INR with a common, broad-spectrum antibiotic such as erythromycin or ciprofloxacin, we must decide whether we need to adjust the dose downward and continue monitoring the patient," says Lynn Oertel, clinical nurse specialist for the anticoagulation management service at Massachusetts General Hospital.

Antiphospholipid Antibodies will throw your INR off!

If you have Antiphospholipid antibodies (lupus anticoagulants) in your body, then you may experience incorrect INR results. There are special INR machines designed to more accurately measure an INR for someone with Antiphospholipid antibodies. It is important to test whether you have Antiphospholipid antibodies so your doctor can take this into account. This is also called Hughes Syndrome.

The APS Foundation of America recommends that if you have APS, then your INRs should be checked from blood drawn from a vein and tested in a laboratory rather than from finger stick machines. It's important that your INR reading is correct, because if you're treated for an incorrect INR, it could have dire consequences.

How Warfarin "thins" the blood

Warfarin, also known by the brand name Coumadin® does not actually "thin" the blood or dissolve clots. Instead, it increases the time your body takes to clot by blocking the clotting factors that let your blood clot. So, after a clot has occurred, the goal of blood thinners is to prevent further extension of the blood clot and prevent future clots. Your body will naturally break down the blood clot while the blood thinner prevents additional clots from forming and prevents current clots from growing or dislodging and getting stuck somewhere else.7 However, saying that is a mouth full, so most often a Warfarin patients' blood is referred to as "thin" or "thick."

In addition, Warfarin does not reverse ischemic tissue damage (damage to your tissue when it is deprived of oxygen from a clot).

Other INR Levels near your INR of 3.8

General INR Levels

Disclaimer: This page is an information resource only and is not to be relied on or substituted for any professional diagnostic or treatment. If you believe you have a blood clot or any other medical condition, you must consult a doctor.

  1. Kuruvilla, Mariamma, and Cheryle Gurk-Turner. "A Review of Warfarin Dosing and Monitoring." Proceedings (Baylor University. Medical Center). Accessed March 27, 2015. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1305837/.
  2. "LABORATORY MONITORING OF ORAL ANTICOAGULANT THERAPY." Utmb Health. Accessed March 27, 2015. http://www.utmb.edu/LSG/Pages/ORAL_ANTICOAG_THERAPY.aspx.
  3. "UC San Diego Health System." UC San Diego Health System. Accessed March 27, 2015. http://health.ucsd.edu/specialties/anticoagulation/providers/warfarin/Pages/dose-adjustments.aspx.
  4. "Drug Information Center." University of Illinois at Chicago. Accessed March 27, 2015. http://dig.pharm.uic.edu/faq/roleofvk.aspx.
  5. "To Bridge or Not to Bridge." University of Texas at Austin. October 7, 2011. Accessed March 27, 2015. https://www.utexas.edu/pharmacy/divisions/pharmaco/rounds/10-07-11rounds2.pdf.
  6. "Protocol Anticoagulation." Rutgers New Jersey Medical School. Accessed March 27, 2015. http://njms.rutgers.edu/departments/medicine/divisions/clinical/guide/protocol.cfm.
  7. "COUMADIN® TABLETS (Warfarin Sodium Tablets, USP) Crystalline COUMADIN® FOR INJECTION (Warfarin Sodium for Injection, USP)." Federal Drug Administration. Accessed March 27, 2015. http://www.accessdata.fda.gov/drugsatfda_docs/label/2010/009218s108lbl.pdf.
  8. Horton JD, Bushwick BM. Warfarin therapy: evolving strategies in anticoagulation. Am Fam Physician. 1999;59:635–646.
  9. Hirsh J, Dalen JE, Anderson DR, Poller L, Bussey H, Ansell J, Deykin D, Brandt JT. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest. 1998;114(5 Suppl):445S–469S.
  10. "Warfarin Maintenance Dosing Nomogram." University of Washington. Accessed March 27, 2015. http://depts.washington.edu/anticoag/home/content/warfarin-maintenance-dosing-nomogram.
  11. "Interactions with COUMADIN." Coumadin®. Accessed March 27, 2015. http://www.coumadin.com/pdf/Interactions_With_COUMADIN.pdf.
  12. "Warfarin Users, Beware of Antibiotics." Harvard Health. Accessed March 27, 2015. http://www.health.harvard.edu/heart-health/warfarin-users-beware-of-antibiotics.
  13. "Food and Supplement Interactions." UC San Diego Health System. Accessed March 27, 2015. http://health.ucsd.edu/specialties/anticoagulation/providers/warfarin/Pages/supplement-interactions.aspx.

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