If you are wondering whether MusclePharm Assault Pre-Workout causes side effects, the maker’s product page lists none. The research on its best-studied ingredient, creatine, reports side effects that are isolated rather than common. A 2007 review of creatine safety found it well tolerated in most people in short-term studies, and most clinical studies it looked at did not find more side effects. The maker calls Assault “University studied and designed for athletes” and says it pairs creatine monohydrate, beta-alanine and caffeine for energy, focus and strength.
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Safety summary
- What is in it: per one scoop (11.5 g): creatine monohydrate 3 g, beta-alanine 1.75 g, betaine anhydrous 1.5 g, taurine 1 g, L-glycine 1 g, caffeine anhydrous 250 mg and acetyl-L-carnitine HCl 250 mg, plus vitamins B6, B12, C and E and 40 mg calcium on the Supplement Facts panel. A separate Nutrition Facts panel on the page shows calcium and potassium for a different serving size, so those amounts are unverified.
- Most commonly reported effects for these ingredients: with caffeine, too much can bring on jitteriness, anxiety and disrupted sleep. With creatine, isolated reports involve muscle, kidney or gut, and most clinical studies found no increase in side effects.
- Medicines to ask about: ACE inhibitor blood pressure medicines, potassium-sparing diuretics, thyroid medicine and certain antibiotics, as named on the general potassium and calcium pages. Ask a pharmacist about blood thinners, diabetes medicines and antidepressants.
- Ask a clinician first: if you are pregnant or breastfeeding, under 18, have surgery planned, have a heart, kidney, liver or bowel condition, or have a milk, egg or soy allergy.
What is in MusclePharm Assault, and what does the research say about each ingredient?
The label lists these amounts per scoop.
| Ingredient and label amount | What the research reports, including side effects |
|---|---|
| Creatine monohydrate, 3 g | A 2007 creatine safety review found creatine well tolerated in most people in short-term studies. It notes isolated reports affecting muscle, kidney or gut, but the majority of clinical studies did not find an increased incidence of side effects. Studies have not found clinically significant changes in kidney, liver, heart or muscle function, and few long-term data exist. A 2015 review reports consistent strength and power gains in short, high-intensity efforts of 30 seconds or less. For more on the human studies, see creatine side effects in human studies (our research library). |
| Beta-alanine, 1.75 g | The maker says it works to buffer lactic acid built up during hard exercise. |
| Betaine anhydrous, 1.5 g | |
| Taurine, 1 g, and L-glycine, 1 g | |
| Caffeine anhydrous, 250 mg | A 2015 review says caffeine has been shown to improve endurance exercise, with mixed results for strength and sprint performance. Too much caffeine can cause jitteriness, anxiety and disrupted sleep. |
| Acetyl-L-carnitine HCl, 250 mg | |
| Calcium, 40 mg on the Supplement Facts panel and 1,038 mg on the Nutrition Facts panel | A 2025 review of calcium supplements in general reports gastrointestinal side effects. The 1,038 mg figure is unverified because the two panels conflict. |
| Potassium, 493 mg on the Nutrition Facts panel | The St. Jude potassium guide lists muscle weakness and abnormal heartbeats among possible side effects of high potassium in the blood. The 493 mg figure is unverified for this formula because it sits on a panel with a different serving size. |
| Silica, listed as silica and calcium silicate | WebMD notes that silica is added to many food products and supplements. |
| Vitamin C, 300 mg | A Singapore retailer’s review says too much vitamin C could cause diarrhea or nausea. That is retailer opinion, not published research. |
| Vitamin B6, 20 mg; vitamin B12, 50 mcg; vitamin E, 36 mg |
The seller’s label panels do not match
The product page shows two different panels. The Nutrition Facts panel is for a 17 fl. oz. serving with 220 calories, 40 g protein, 290 mg sodium and 1,038 mg calcium. The Supplement Facts panel is for one 11.5 g scoop. Because the serving sizes differ, check the panel on the tub you receive, and ask the seller which one applies to Assault before you count calories or minerals. For another walk through reading ingredient labels, see our research labs peptides ingredients guide.
Common side effects, and what usually helps
For caffeine, the common complaints are jitteriness, anxiety and sleep trouble. If you are new to caffeine, ask a pharmacist whether starting with less makes sense for you.
With creatine, the research points to stomach, kidney or muscle complaints that are isolated rather than common. A 2015 review suggests that stomach side effects from taking caffeine and creatine together may be one explanation for a possible blunting of creatine’s effect.
If calcium upsets your stomach, the NDSU Extension calcium guide says constipation or stomach upset may ease with more fluid or a different calcium type. If itching or tingling is your concern, our Why Pre-Workout Makes You Itch: Beta-Alanine Safety Guide covers why pre-workout can make you itch.
Which medicines interact with these ingredients?
The potassium and calcium interactions below come from general potassium and calcium pages, not from research on creatine, caffeine or beta-alanine. Whether they apply to you depends on which label panel is correct for your tub.
| Medicine | Why it matters | Source |
|---|---|---|
| ACE inhibitors such as lisinopril, enalapril, captopril and benazepril | Can raise potassium in the blood. | St. Jude potassium guide |
| Potassium-sparing diuretics such as triamterene and spironolactone, and albuterol | Can raise potassium in the blood. | St. Jude potassium guide |
| Thyroid medicine such as levothyroxine | Calcium can reduce absorption when taken around the same time. This scoop lists 40 mg calcium on the Supplement Facts panel, a small amount. | Kaiser Permanente calcium entry |
| Quinolone and tetracycline antibiotics such as ciprofloxacin, levofloxacin, doxycycline and minocycline | Calcium can reduce absorption when taken around the same time. | Kaiser Permanente calcium entry |
| Bisphosphonates such as alendronate, and penicillamine | Calcium can reduce absorption when taken around the same time. | Kaiser Permanente calcium entry |
The St. Jude potassium guide and the Kaiser calcium entry do not name blood thinners, diabetes medicines or antidepressants. Ask a pharmacist to check those against the full label before your first scoop.
Who should ask a clinician first?
- Pregnant or trying to get pregnant: If you are pregnant, ask your clinician before using any pre-workout. Kaiser’s calcium entry says to tell your doctor if you are pregnant before using calcium products, and the MSKCC potassium sheet says to talk through benefits and risks if you are pregnant, planning to be, or breastfeeding.
- Breastfeeding: the same Kaiser entry says to consult your doctor before breastfeeding.
- Under 18: ask a doctor first.
- Surgery planned: tell your surgeon or dentist about every product you use, including herbal products, as the Kaiser entry advises.
- Heart, blood vessel, kidney, liver or bowel conditions: the Kaiser entry lists heart and blood vessel disease, kidney disease including kidney stones, liver disease and certain bowel diseases as conditions to tell your doctor about. The Cleveland Clinic’s potassium binder page notes that chronic kidney disease raises the risk of high potassium.
- Allergies: the label says it contains milk, egg and soy (lecithin), and is made in a facility that may also process tree nuts, sesame, peanuts, fish, crustaceans, shellfish and wheat.
How should I start, and when should I contact a clinician?
Follow the maker’s directions: mix one scoop (11.5 g) in 8 to 12 fl. oz. of cold water and drink it 20 to 30 minutes before training. The product page says not to exceed one serving per day.
St. Jude’s potassium guide lists muscle weakness and abnormal heartbeats among signs of high potassium in the blood, and allergic reaction symptoms such as rash, hives, itching, swelling of the face or neck, and shortness of breath. If you notice any of these, contact a clinician the same day. For swelling of the face or throat or trouble breathing, get emergency help right away. You can report side effects through the FDA MedWatch reporting page.
What time is too late to drink pre-workout, and what cancels it out?
Caffeine can disrupt sleep, so if you train late in the evening, a lower-caffeine or stim-free option may suit you better. A pharmacist can advise on timing alongside your other medicines.
On what cancels out a pre-workout, a 2015 review says scarce research suggests caffeine may blunt creatine’s effect. Its authors suggest this may come from opposing effects on muscle relaxation time or from stomach side effects when the two are taken together.
Why am I always tired, even when I sleep a lot?
The NIH’s MedlinePlus says fatigue is a symptom rather than a disease. It can be a normal response to physical activity, emotional stress, boredom or lack of sleep. If you have been tired for weeks, contact your health care provider, who can help find the cause. Healthline lists other common reasons for tiredness, including shift work and a less active lifestyle. Check the MedlinePlus fatigue page for more.
How much does muscle pharm assault preworkout cost, and how do I buy it?
Prices as of November 3, 2026; check the checkout for today’s.
| Package | Price | What is included |
|---|---|---|
| One tub, 30 servings | $34.99 | Choice of flavor: Fruit Punch, Blue Raspberry, Watermelon, Melon Hwachae or Sour Peach Rings. The page offers one-time or subscription purchase. |
Check today’s price and flavors on the seller’s Product Page. The page also shows a discount box with blank price fields, so confirm the final total in your cart.
Refunds, cancellation and shipping
Check the seller’s returns and cancellation terms at checkout before you pay. If you use an HSA or FSA, the page says Flex, its HSA/FSA payment option, is available for eligible customers.
Before you order
- Check which label panel applies to the tub you receive, and ask the seller which one is correct.
- Look up the refund window, subscription cancellation and shipping time at checkout.
- Share your medicine list with a pharmacist, including blood thinners, diabetes medicines and antidepressants.
- If you have a milk, egg or soy allergy, or any other condition on the list above, check with your clinician first.
- Our olivaro side effects and safety guide includes a medicine checklist you can adapt for this product.
- Bring the label and your medicine list to your next primary care visit.
By the Primary Care Evidence Guide Team