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Dietary supplement

TestoJack 300 Ingredients & Drug Interactions

by NOW

TestoJack 300 label
See full label image
Capsule Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking TestoJack 300 against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

TestoJack 300 is a dietary supplement by NOW with 1 active ingredient. Its ingredients are commonly taken for low testosterone or low libido in men, male fertility support, athletic performance and muscle strength.Based on those ingredients, 248 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Tongkat Ali. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against TestoJack 300 by NOW

Ask about any prescription or over-the-counter medication and we check it for interactions with TestoJack 300 by NOW — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of TestoJack 300 by NOW

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

TestoJack 300 contains one active ingredient: tongkat ali (Eurycoma longifolia root extract). The capsule also holds inactive ingredients — microcrystalline cellulose, hypromellose, silicon dioxide, and magnesium stearate — which are binders and fillers that help deliver the active ingredient.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: men's support and testosterone health.
  • We looked for evidence on: Age-related testosterone deficiency, Athletic performance, Muscle strength, Sexual desire, Male Infertility, Erectile dysfunction (ED) — and 3 related terms.
  • The strongest evidence on file: Eurycoma Longifolia is rated "Possibly Effective" for Sexual desire (Natural Medicines).
  • Also on file: Eurycoma Longifolia is rated "Possibly Ineffective" for Athletic performance.
  • Also on file: Eurycoma Longifolia is rated "Insufficient Reliable Evidence To Rate" for Erectile dysfunction (ED), Muscle strength, Age-related testosterone deficiency, Male Infertility.

Tongkat ali is possibly effective for sexual desire based on the research we've reviewed. For athletic performance, the evidence suggests it's possibly ineffective.

The data on back pain, osteoporosis, and diabetes isn't reliable enough to rate, so we can't tell you whether it works for those purposes.

The evidence, ingredient by ingredient Eurycoma Longifolia

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Tongkat ali is generally tolerated in short-term studies, but we don't have solid information on long-term safety or how consistent product quality is across brands. The ingredient may raise testosterone levels — and if they go too high, you could see acne, insulin resistance (blood sugar control problems), liver stress, and other testosterone-related side effects.

Because of hormonal effects and limited safety data, avoid this product during pregnancy and while breastfeeding.

Side effects, ingredient by ingredient Eurycoma Longifolia

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Eurycoma Longifolia.
  • The most serious interaction on file is rated Moderate.
  • For scale: 248 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Check before using if you take propranolol (Inderal) or other beta-blockers — tongkat ali can reduce how well they work. Also double-check any testosterone replacement or hormone therapy, any drugs processed through your liver's CYP1A2, CYP2C19, or CYP2A6 pathways, and any medications that depend on those liver enzymes to work.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

If you're looking to support sexual desire and don't take propranolol or other medications metabolized by your liver, this might be worth a conversation with your pharmacist. Anyone on beta-blockers, testosterone therapy, or drugs processed through CYP1A2, CYP2C19, or CYP2A6 should check their specific medications first.

Pregnant or breastfeeding? Skip it.

Talk with us before you start.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Aug 22, 2024.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about TestoJack 300, straight from the product label.

Brand NOW
Barcode (UPC) 733739022028
Net contents 60 Veg Capsule(s)
Market status On market
Date entered into DSLD Aug 22, 2024
DSLD ID 314136
Product type Botanical
Supplement form Capsule
Dietary claims / uses All Other, Structure/Function
Intended target group(s) Vegan, Vegetarian, Kosher, Adult Male (18-50 Years), Gluten Free, Dairy Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for TestoJack 300 by NOW, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Veg Capsule(s)
Maximum serving Sizes:
1 Veg Capsule(s)
Servings per container
60
UPC/BARCODE
733739022028
IngredientAmount% DV
Tongkat Ali300 mg--

Other ingredients: Microcrystalline Cellulose, Hypromellose, Silicon Dioxide, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Suggested Usage: Take 1 capsule daily as needed, or as recommended by your healthcare practitioner.

Formula

Eurycoma longifolia Jack is the scientific name for what is more commonly known as Tongkat ali, Malaysian ginseng, or longjack. Although every part of the Tongkat Ali plant is used by traditional herbalists of Southeast Asia, its root is especially prized. Tongkat Ali is known to possess various naturally occurring bioactive compounds, including eurypeptides and saponins. NOW TestoJack 300 delivers 300 mg non-GMO Tongkat ali extract per capsule.

TestJack 300 with 300 mg of Tongkat Ali (Eurycoma longifolia Jack Extract)

Men’s Support Formula

Triangle K (Kosher)

FDA Disclaimer Statement

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Precautions

Caution: For adults only. Keep out of reach of children.

This product is not intended for those with a serious medical condition or pregnant/nursing women. Consult your physician if taking any medication.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.

Formulation

Non-GMO

Vegetarian/Vegan

Made and quality tested in the USA with globally sourced ingredients.

Not manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish, tree nut or sesame ingredients.

Natural color variation may occur in this product.

FDA Statement of Identity

A Dietary Supplement

Seals/Symbols

Triangle K (Kosher)

GMP Quality Assured

General Statements

Botanicals/Herbs Family owned since 1968.

Storage

Store in a cool, dry place after opening.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

TestoJack 300 by NOW label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

TestoJack 300 label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in TestoJack 300 by NOW

This is the 1 active ingredient this product is made of. Select it to open its full monograph.

Serving size1 Veg Capsule(s) Dosage formCapsule Servings per container60 Amounts shown are per serving.

Tongkat Ali

Interacts with
248 drugs
300 mg per serving Form: Eurycoma longifolia jack extract

Eurycoma longifolia (tongkat ali) is a Southeast Asian herb most popular for supporting testosterone, libido, and male fertility, with some small huma...

Tongkat Ali monograph & interactions

Other (inactive) ingredients: Microcrystalline Cellulose, Hypromellose, Silicon Dioxide, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

TestoJack 300 by NOW Drug Interactions

Want to check YOUR meds against TestoJack 300?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
248Drugs
3 Moderate 245 Minor

Ingredients driving the most interactions

Tongkat Ali 248

Individual Drug Interactions

The ingredients in TestoJack 300 interact with 248 drugs. Click any drug to see the details.

1 of the 1 ingredient in TestoJack 300 interact with drugs. Each result below shows which ingredient is responsible. Tongkat Ali

Each ingredient & the kinds of drugs it affects

For each ingredient in TestoJack 300 with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Tongkat Ali5 drug types · 248 drugs

Propranolol (Inderal)

Eurycoma longifolia can reduce the levels and clinical effects of propranolol.
A small clinical study in healthy persons shows that taking a single dose of a water-based Eurycoma longifolia extract 200 mg, in combination with a single dose of propranolol 80 mg, reduces the propranolol area under the curve (AUC) by 29%, reduces the peak concentration by 42%, and increases time to peak concentration by 86% when compared with control. Since the elimination half-life of propranolol did not change, it seems that Eurycoma longifolia alters the kinetics of propranolol by decreasing its absorption in the gut, and not by altering its metabolism. It is not known if separating administration will prevent this interaction.

Likelihood Probable Evidence A
Cytochrome P450 1A2 (Cyp1A2) Substrates

Theoretically, Eurycoma longifolia might increase levels CYP1A2 substrates.
In vitro research suggests that methanolic Eurycoma longifolia root extract weakly inhibits CYP1A2 enzymes. This effect has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2A6 (Cyp2A6) Substrates

Theoretically, Eurycoma longifolia might increase levels of CYP2A6 substrates.
In vitro research suggests that methanolic Eurycoma longifolia root extract weakly inhibits CYP2A6 enzymes. This effect has not been reported in humans.

Likelihood Possible Evidence D
Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, Eurycoma longifolia might increase levels of CYP2C19 substrates.
In vitro research suggests that methanolic Eurycoma longifolia root extract weakly inhibits CYP2C19 enzymes. This effect has not been reported in humans.

Likelihood Possible Evidence D
Testosterone

Theoretically, Eurycoma longifolia may further increase levels of testosterone.
A clinical study in aging males with testosterone levels below 300 ng/dL shows that taking a specific water extract of Eurycoma longifolia roots (Physta; Biotropics Malaysia) 100-200 mg daily with breakfast for 12 weeks increases total testosterone levels by 8% to 11% when compared with placebo. It is unclear whether this increase would occur in individuals with normal testosterone levels.

Likelihood Possible Evidence D
Tongkat Ali full monograph & interactions
The maker

Brand information

Manufacturer and brand details for TestoJack 300, from the product label.

NOW

See all NOW products
Name
NOW Foods
Street Address
395 S. Glen Ellyn Rd.
City
Bloomingdale
State
IL
ZipCode
60108
Web Address
nowfoods.com
Pharmacist Counseling Corner

TestoJack 300 by NOW: Common Questions

Does TestoJack 300 by NOW interact with any medications?
Yes. Based on its ingredients, TestoJack 300 has a known interaction with 248 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
TestoJack 300 contains a single active ingredient, and that one ingredient can interact with many different medications on its own. We check it against each medication and show the mechanism responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Does tongkat ali really boost testosterone?
Research in men with low testosterone shows it can raise levels by about 8% to 10% over 12 weeks. That's a modest boost, not a dramatic one — and it depends on you starting with naturally low levels. If your testosterone is already normal or high, raising it further could cause acne, liver stress, or blood sugar problems.
Can I take this while pregnant or breastfeeding?
No. There isn't enough safety data and tongkat ali's hormonal effects mean it's best to avoid it during pregnancy. We also don't have reliable safety information for breastfeeding, so skip it then too. Talk with your doctor if you're planning pregnancy or nursing.
How long can I safely take TestoJack 300?
The studies we have are short-term, so we know it's generally tolerated for a few weeks or months. We don't have solid data on long-term safety, so this is something to discuss with your pharmacist or doctor if you're thinking about taking it for months on end.
Will this interact with my blood pressure medication?
If you take propranolol (Inderal) specifically, yes — tongkat ali can lower its levels by about 29%, which may make it less effective at controlling your blood pressure. Other blood pressure drugs may have different interactions, so check your exact medication with the tool on this page.
What is tongkat ali used for?
Tongkat ali is the active ingredient in this product — it's an extract from the Eurycoma longifolia root. It's been studied mostly for sexual desire, where the evidence supports it as possibly effective.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

TestoJack 300 label
Go deeper

The Full Monographs Behind TestoJack 300’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Eurycoma Longifolia

Interacts with 248 drugs

Eurycoma longifolia (tongkat ali) is a Southeast Asian herb most popular for supporting testosterone, libido, and male fertility, with some small human studies suggesting possible benefits....

Read the full Eurycoma Longifolia monograph →
Sources

Sources & How We Checked

TestoJack 300's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 4 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Eurycoma Longifolia 4 references
  1. Salman SA, Amrah S, Wahab MS, et al. Modification of propranolol's bioavailability by Eurycoma longifolia water-based extract. J Clin Pharm Ther 2010;35:691-6. PubMed
  2. Tambi MI, Imran MK, Henkel RR. Standardised water-soluble extract of Eurycoma longifolia, Tongkat ali, as testosterone booster for managing men with late-onset hypogonadism? Andrologia 2011 Jun 15. doi: 10.1111/j.1439-0272.2011.01168.x. [Epub ahead of pri PubMed
  3. Han YM, Kim IS, Rehman SU, Choe K, Yoo HH. In vitro evaluation of the effects of Eurycoma longifolia extract on CYP-mediated drug metabolism. Evid Based Complement Alternat Med 2015;2015:631329.
  4. Chinnappan SM, George A, Pandey P, Narke G, Choudhary YK. Effect of Eurycoma longifolia standardised aqueous root extract-Physta ® on testosterone levels and quality of life in ageing male subjects: a randomised, double-blind, placebo-controlled multicent

See these in context on the Eurycoma Longifolia monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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