International Normalised Ratio (INR)#

An INR below your target range means your blood is clotting more quickly than the medication is supposed to allow. This increases the risk of a stroke (in atrial fibrillation or mechanical valves) or a new blood clot (after DVT or pulmonary embolism).

What usually happens next:

• Your prescribing clinician will review and may increase your blood-thinner dose.
• You will likely have an earlier repeat INR (often in 1 to 2 weeks).
• You will be asked about recent changes - new medications, diet changes, missed doses, vomiting, diarrhea.

An INR above your target means your blood is taking longer than intended to clot. This increases bleeding risk.

• Slightly above range (e.g., target 2 to 3, INR 3.2 to 3.5): usually a dose adjustment by your prescribing clinician without urgent action.
• Significantly above range (INR 4.5 to 10): more careful management, possibly holding a dose or two.
• INR above 10 OR any active bleeding: medical urgency - please go to urgent care or the emergency department right away.

Common reasons for an unexpectedly high INR:

• New antibiotic
• New non-prescription anti-inflammatory (ibuprofen, naproxen) or prescription anti-inflammatory
• New supplement (cranberry, fish oil, ginkgo, garlic, vitamin K changes)
• New prescription antifungal or antiviral
• Illness, especially with reduced food intake
• Less leafy-green vegetables than usual (lower vitamin K intake raises INR)
• Heavy alcohol use

The standard cadence:

• Just starting therapy or after a dose change: every few days to weekly until stable
• Stable, consistent INR in range: every 4 to 6 weeks (most patients)
• Long-standing stable INR (over 6 months in range): some guidelines allow up to every 12 weeks - check with your prescribing clinician
• New medication, illness, or dose change: within 5 to 7 days
• Travel, big diet change: consider an earlier check after returning

No. The newer oral blood thinners (a class sometimes called DOACs - direct-acting oral anticoagulants) do not require INR monitoring. They are dosed based on kidney function, weight, and age, with periodic checks of kidney function and blood count (CBC) instead. If your prescribing clinician has switched you to one of these newer medications, you no longer need INR monitoring.

INR is very sensitive to several factors:

Medications that often raise INR (more bleeding risk):

• Most antibiotics
• Some antifungal medications
• Some antiviral medications
• Some heart-rhythm medications
• Some thyroid medications
• Some prescription anti-inflammatory medications

Medications and substances that often lower INR (less protection):

• Some anti-seizure medications
• Some tuberculosis medications
• St. John's wort (herbal)
• High vitamin K intake (large amounts of kale, spinach, broccoli, Brussels sprouts)

Other factors:

• Illness, especially with vomiting or diarrhea
• Heavy alcohol use
• Major diet changes
• Recent travel across time zones (dose timing changes)
• Pregnancy - this medication is generally not used in pregnancy

If you start ANY new medication or supplement while on this blood thinner, please let your prescribing clinician know and arrange an INR within a week.

"Therapeutic" means your INR is within the target range set by your clinician for your specific reason for being on the medication. For most atrial-fibrillation patients, that is 2.0 to 3.0. For mechanical mitral valves, it is 2.5 to 3.5. Time in therapeutic range (TTR) is a quality measure - well-managed patients spend more than 65 to 70% of their time in range.

Some patients have INR that swings widely from visit to visit despite no obvious reason. Causes include:

• Genetic variation in how your liver processes the medication
• Inconsistent timing of doses
• Inconsistent diet
• Frequent illness or medication changes
• Underlying liver, kidney, or thyroid issues

If your INR is consistently unstable, your prescribing clinician may discuss switching to a newer oral blood thinner (if your reason for being on this medication allows it) or refer you to an anticoagulation clinic for more intensive monitoring.

Mechanical valves carry a higher risk of forming clots on the valve itself, especially mitral valves. They require a higher INR target (typically 2.5 to 3.5) to keep that risk acceptably low. Most mechanical-valve patients cannot be switched to a newer oral blood thinner - the vitamin-K-antagonist medication remains the standard.

Sometimes yes, but only on your prescribing clinician's advice. The combination increases bleeding risk significantly and is typically only used in specific situations (e.g., after recent stent placement or in select mechanical-valve patients). Do not start aspirin on your own while on a blood thinner.

This depends on:

• The type of procedure (minor dental work usually does not require stopping)
• Your bleeding and clotting risk
• Your indication for the blood thinner

Most dental cleanings and simple extractions can be done without stopping the medication. More invasive procedures (colonoscopy with polyp removal, surgery) typically require coordination between your surgeon and your prescribing clinician, sometimes with a temporary switch to short-acting injectable blood thinners ("bridging").

Please consult your prescribing clinician at least 1 to 2 weeks before any procedure.

The vitamin-K-antagonist blood thinner can harm a developing baby, especially in the first trimester. If you are pregnant or planning to become pregnant, please discuss with your prescribing clinician right away. Most patients are switched to injectable blood thinners (which do not cross the placenta) during pregnancy.

TeleTest does not currently manage pregnancy care - please see your obstetric provider for pregnancy-related anticoagulation management.

If your INR is significantly outside your target range, a TeleTest clinician may:

• Contact you to make sure you are not bleeding and to review your recent medications, illness, and diet
• Ask you to contact your prescribing clinician promptly for dose adjustment
• Recommend you go to urgent care or the emergency department if the INR is very high (above 10) or you have active bleeding
• Schedule an earlier repeat INR

TeleTest can adjust the dose of this medication based on your INR result. If you're already followed by an anticoagulation clinic or specialist for ongoing management, you may prefer to keep dose changes with that team for continuity.