Both take 4 capsules per serving, and both are built on D-aspartic acid and KSM-66 ashwagandha. Where they part ways is dosing and the added ingredients.
In some ways the two are alike. Each serving of 4 capsules delivers about 2 grams of D-aspartic acid and 4,000 IU of vitamin D. Testosil pulls ahead on KSM-66 ashwagandha (300 mg vs 200 mg), zinc and ginseng, and also has L-arginine and garlic. Testogen doubles the fenugreek, brings boron, nettle, vitamin K2 and copper, and holds zinc to a more comfortable 25 mg. As finished products, neither has been put through a clinical trial.
Amounts below are for a 4-capsule serving. We read Testogen's from the supplement facts at testogen.com (checked October 2026). Testosil's facts panel is an image, so instead we used the label amounts in the Certificate of Analysis that its homepage links to (Dyad Labs, April 2024).
| Ingredient | Testosil | Testogen |
|---|---|---|
| D-aspartic acid | 2,000 mg | 2,025 mg |
| KSM-66 ashwagandha | 300 mg | 200 mg |
| Fenugreek seed extract | 50 mg | 100 mg |
| Asian / Korean ginseng (Panax ginseng) | 180 mg | 100 mg |
| Stinging nettle root | None | 80 mg |
| L-arginine HCl | 250 mg | None |
| Garlic extract | 24 mg | None |
| Absorption aid | AstraGin, 10 mg | BioPerine (black pepper), 7 mg |
| Zinc | 40 mg | 25 mg |
| Magnesium | 50 mg | 100 mg |
| Vitamin D3 | 100 mcg (4,000 IU) | 100 mcg (4,000 IU) |
| Vitamin B6 | Around 5.6 mg | 8 mg |
| Vitamin B5 (pantothenate) | 8 mg | None |
| Vitamin K2 (MK-7) | None | 90 mcg |
| Boron | None | 5 mg |
| Copper | None | 0.5 mg |
| Recommended use | 1 to 2 servings daily | 1 serving daily (2 capsules at breakfast, 2 at lunch) |
A note on Testosil: its certificate is from a 2023 batch, so read the label on your own bottle in case the formula has been changed.
Of everything in these formulas, KSM-66 has the best testosterone data. Wankhede et al. (2015) enrolled 57 men aged 18 to 50 who were on a resistance training program. They took 300 mg twice a day or placebo for 8 weeks, and testosterone went up about 96 ng/dL on ashwagandha against 18 ng/dL on placebo. Caveats: the extract came from its manufacturer and the trial was small.
One serving of Testosil gives 300 mg, which equals one of the two daily doses used in the KSM-66 study. Two servings would reach the full 600 mg. Two servings would double zinc to 80 mg and vitamin D to 8,000 IU a day, twice the adult upper limits, so don't take two servings without a doctor's advice. Testogen's 200 mg sits below what was studied.
Each supplies about 2 grams, and the evidence is weak. In a 2015 trial of 24 resistance-trained men, 3 g a day left testosterone unchanged over two weeks, and 6 g a day lowered it. The doses are nearly the same and neither is well supported, so this ingredient shouldn't decide your choice.
Rao et al. (2016) is the best-known fenugreek trial. It gave 120 men aged 43 to 70 a standardized extract at 600 mg a day for 12 weeks, and it reported higher testosterone and better aging-male symptom scores. The extract's maker funded the work. Testogen has a sixth of that dose at 100 mg, and Testosil a twelfth at 50 mg. Neither is likely to deliver much from fenugreek.
Each provides 4,000 IU of vitamin D, a high amount for daily use. Testosil's 40 mg of zinc is high too, while Testogen's 25 mg is more moderate. This matters if you use a multivitamin or follow Testosil's two-serving option, which doubles both nutrients. Testogen also includes a little copper, because zinc and copper compete for absorption. Our Testosil side effects guide goes into the upper limits.
Boron, nettle root and vitamin K2 are in Testogen. Evidence for them on testosterone is limited and mixed, so treat them as minor extras and not a reason to buy. Testosil's L-arginine and garlic are meant more for blood flow than testosterone, and at these doses any effect is probably small. For a wider way to judge formulas like these, our guide to choosing a testosterone supplement explains what to look for.
| Testosil | Testogen | |
|---|---|---|
| One month | About $69 | About $70 |
| Larger packs | 3 bottles about $177, or 6 bottles about $294 | 3 bottles about $140, or 5 bottles about $210 |
| Guarantee | "Lifetime": refund covers unopened bottles and one opened bottle, with shipping excluded and one order per customer | 100 days: refund covers unopened bottles and one opened bottle |
| Seller | Leading Edge Health (addresses listed in Canada, Cyprus and the U.S.) | testogen.com shows no company name or address |
Prices were noted in October 2026 and move often. When we looked, Testogen's packages were out of stock. Neither guarantee covers more than one opened bottle, so you can't test six bottles and expect a full refund. Testosil's has no time limit, the more generous feature. Some wording on its guarantee page is inconsistent, however, so confirm the terms before you return anything.
A third-party lab certificate is also available for Testosil. It confirms the batch matched its label and tested negative for hidden drugs, including sildenafil and SARMs. For Testogen, we found no similar certificate on testogen.com.
Much of the safety profile is shared, since the core ingredients overlap. Both formulas have ashwagandha, which is tied to rare liver injury and thyroid hormone changes and may interact with diabetes, thyroid, blood pressure, sedative and immunosuppressant medicines. Both also have ginseng and fenugreek, either of which can lower blood sugar. Testosil carries a little more risk to weigh, given the bigger ashwagandha dose and the garlic, which may raise bleeding risk with blood thinners.
Check with a doctor before taking either product if you have hormone-sensitive prostate cancer, liver disease or a thyroid condition. For Testosil's risks in detail, see our guide to Testosil side effects.
Considering a formula that doesn't center on D-aspartic acid? Look at our Testosil vs TestRX comparison.
The two products are close cousins. In Testosil's favor are a bigger dose of KSM-66 ashwagandha, the ingredient with the most testosterone research, a longer guarantee and a published lab test. Testogen's strengths are a milder zinc dose, a little more fenugreek and magnesium, and additional micronutrients.
Without a clinical trial on either product, the realistic expectation is a modest effect at most, mainly from the ashwagandha and from making up any vitamin D or zinc shortfall. Neither is a treatment for low testosterone. Our Testosil review has the full verdict on value.
Affiliate link: if you buy through it, we earn a commission at no extra cost to you. The guarantee is advertised as a lifetime money-back offer. It refunds unopened bottles and one opened bottle, doesn't refund shipping, and allows one order per customer. Parts of the guarantee page are worded inconsistently, so check the terms with customer service before returning anything.