DIM, short for 3,3′-diindolylmethane, does change urine color for a significant number of people who take it. In a double-blind controlled trial, about a third of women taking DIM supplements reported darkening of their urine, compared with only one in ten on a placebo. The color shift is typically described as a deeper amber, brownish, or sometimes slightly orange tone, and it stems from the way your body breaks down and excretes the indole-based compounds in DIM. The change is considered a harmless side effect, but it catches many first-time users off guard.
How Common the Color Change Actually Is
Anecdotal reports of dark urine from DIM supplements are everywhere online, but the best quantified estimate comes from a randomized, placebo-controlled trial involving women taking DIM for cervical health. In that study, 31% of women receiving DIM reported darkened urine, compared with 10% of women on placebo. That gap was statistically robust. Aside from the urine change, the rate of other non-serious side effects was only modestly higher in the DIM group than in the placebo group.1British Journal of Cancer. Effect of diindolylmethane supplementation on low-grade cervical cytological abnormalities: double-blind, randomised, controlled trial
Two things stand out here. First, a third is a lot of people, which explains why this question is so common among DIM users. Second, one in ten placebo users also noticed darker urine, which is a reminder that day-to-day urine color fluctuates for all sorts of reasons, from hydration levels to diet. Still, DIM clearly pushes the odds of noticeably darker urine well above baseline.
Why DIM Darkens Urine
DIM is an indole compound, and the chemistry of indoles helps explain the color shift. DIM forms in your stomach from indole-3-carbinol (I3C), a compound found in cruciferous vegetables like broccoli and Brussels sprouts. Once absorbed, DIM and related indole metabolites undergo extensive processing in the liver, where cytochrome P450 enzymes oxidize them. These oxidation reactions are the same family of reactions that, in other contexts, convert the simpler indole molecule (a byproduct of gut bacteria breaking down tryptophan) into indoxyl, which gets conjugated to sulfate and excreted in urine as indoxyl sulfate.2PubMed. Oxidation of indole by cytochrome P450 enzymes
Further oxidation and chemical coupling of indoxyl can produce indigoid pigments, including indigo (blue) and indirubin (reddish). These are the same class of pigments that give the dye indigo its famous deep blue color. When DIM supplements flood your system with indole-derived compounds, more of these colored metabolites end up in your urine. The result is not bright blue, because the metabolites are mixed with the normal yellow urochrome pigment that gives urine its usual color. Instead, the combination tends to look darker, sometimes with a brownish or amber cast that people describe in various ways.
The color, then, is not DIM itself passing through unchanged. It is the downstream products of your liver processing a large dose of indole-based material. Your kidneys filter those metabolites into the urine, and the pigmented ones tint it.
Supplements Versus Cruciferous Vegetables
If DIM comes from broccoli and Brussels sprouts, you might wonder why a plate of roasted cruciferous vegetables does not turn your urine dark. The answer is dose. Research measuring urinary DIM levels found that taking I3C supplements produced urinary DIM concentrations roughly 5,000 times greater than what showed up after eating Brussels sprouts.3Cancer Epidemiology, Biomarkers & Prevention. Urinary 3,3′-Diindolylmethane: A Biomarker of Glucobrassicin Exposure and Indole-3-Carbinol Uptake in Humans
That enormous difference explains why the color change is essentially a supplement phenomenon. Eating a normal or even generous amount of broccoli provides so little DIM precursor that the tiny quantity of colored metabolites produced is invisible against the background of your normal urine pigments. When you take a concentrated DIM capsule, the sheer volume of indole metabolites being processed and excreted crosses the threshold where you can see the change with the naked eye. It also means that if you notice dark urine while eating a cruciferous-heavy diet but not taking supplements, DIM is probably not the cause, and you should look at other explanations like hydration or other foods.
Is the Color Change a Sign of Harm?
The dark urine from DIM is consistently described in clinical research as a cosmetic nuisance, not a health warning. In a pharmacokinetic study of healthy adults, no DIM-related adverse effects appeared at doses up to 200 mg. At 300 mg, one of six subjects experienced mild nausea and headache, and one had vomiting, but all events were classified as mild and self-limiting, requiring no treatment.4Cancer Epidemiology, Biomarkers & Prevention. Single-Dose Pharmacokinetics and Tolerability of Absorption-Enhanced 3,3′-Diindolylmethane in Healthy Subjects
The kidney specifically has been evaluated. In an animal safety study of DIM, researchers found no appreciable difference in kidney histology or serum chemistry markers between DIM-treated and control groups.5PubMed Central. A controlled safety study of diindolylmethane in the immature rat model The colored metabolites passing through your kidneys do not appear to damage or irritate the renal tissue. Your kidneys are simply doing their job, filtering waste products from the blood and excreting them. The pigmented indole metabolites happen to be visible, but they are being handled the same way your kidneys handle thousands of other metabolic byproducts every day.
That said, “not harmful at studied doses” is not the same as “take as much as you want.” DIM supplements are not FDA-regulated drugs, and long-term safety data at high doses is limited. If you experience symptoms beyond darkened urine, such as persistent gastrointestinal distress, skin changes, or anything that feels systemic, it is worth backing off the dose and talking to a healthcare provider.
When Dark Urine Is Not From DIM
Here is where the conversation shifts from “this is normal” to “pay attention.” Dark or discolored urine has a long list of potential causes, and attributing every color change to a supplement you happen to be taking is a mistake that can delay recognition of something more serious. Red or brown urine can signal blood in the urine (hematuria), which can be caused by urinary tract infections, kidney stones, or, more rarely, cancers of the bladder or kidney. Very dark brown urine can indicate liver problems or severe dehydration. Certain medications, including some antibiotics and laxatives, also shift urine color dramatically.
One practical trap worth knowing about involves urine dipstick tests. If you visit a doctor and they dip a test strip in your urine sample, some colored metabolites can trigger a false positive on the heme (blood) portion of the strip. A study of dipstick results found that positive heme readings should always be confirmed with a microscopic urinalysis before a patient is referred for urological evaluation, because false positives from pigments and other substances are common enough to generate unnecessary consultations.6PubMed. Dipstick pseudohematuria: unnecessary consultation and evaluation If you are taking DIM and a routine urine test flags blood, mention the supplement to your doctor. It does not mean the result is definitely false, but it means a confirmatory step under the microscope is warranted before anything more invasive.
A sensible rule of thumb: if you started DIM and your urine darkened within a day or two, and the change is consistent and painless, DIM is the overwhelmingly likely explanation. If the color change appeared before you started DIM, if it is accompanied by pain or burning, if you see obvious red or pink rather than amber-brown, or if it persists after you stop taking the supplement, treat it as a separate medical question.
How Hydration Plays Into It
Hydration status acts as a volume dial on whatever pigments are already in your urine. Research using objective colorimetry found that as urine becomes more concentrated from dehydration, it gets significantly darker and more intensely yellow. Interestingly, at moderate levels of dehydration, a slight green hue appeared in the measurements, while more severe dehydration pushed the color further toward a deep yellow-amber.7Frontiers in Nutrition. The Effect of Hydration on Urine Color Objectively Evaluated in CIE L*a*b* Color Space
This matters for DIM users because the supplement’s color-changing metabolites and dehydration are additive. If you take a DIM capsule and then do not drink much water for several hours, the urine you produce will be both more concentrated and more heavily pigmented by indole metabolites. The result can look alarmingly dark. Staying well-hydrated will not eliminate the DIM-related color change, since the metabolites are still there, but it dilutes them enough to make the change less dramatic. Many DIM users report that their first morning urine is the darkest, which makes sense because overnight you are fasting and not drinking fluids, so urine concentration peaks.
What DIM Actually Does in the Body
Most people taking DIM supplements are not taking them for fun. DIM has gained popularity primarily for its effects on estrogen metabolism, and that is the reason most clinical studies have examined it. In premenopausal women, DIM supplementation significantly altered the concentrations of nearly every urinary estrogen and estrogen metabolite measured, with the ratio of 2-hydroxyestrone to 16-hydroxyestrone increasing significantly.8PubMed Central. Exploring the impact of 3,3′-diindolylmethane on the urinary estrogen profile of premenopausal women That particular ratio shift is the one DIM proponents point to most frequently, because 2-hydroxyestrone is generally considered a less potent estrogen metabolite, while 16-hydroxyestrone is more active. The theory is that nudging the ratio in favor of the less potent pathway could be beneficial for conditions influenced by estrogen, including certain breast and cervical concerns.
Whether that metabolic shift translates to meaningful clinical outcomes is where the picture gets hazier. Some studies have explored DIM for cervical dysplasia, breast health, prostate concerns, and hormonal acne, but the evidence base is still relatively thin compared to established pharmaceuticals. What the estrogen metabolism data does confirm is that DIM is biologically active at supplement doses. It is genuinely doing something in your body, not just passing through. The urine color change is, in a roundabout way, proof of that metabolic activity: your liver is working hard to process the indole compounds, and the colored waste products are visible evidence of that work.
Other Supplements and Foods That Change Urine Color
DIM is far from the only thing that can change your urine color, and knowing the common culprits helps you sort through what is happening if your urine looks unusual. B vitamins, especially riboflavin (B2), are famous for turning urine a bright, almost fluorescent yellow. This happens because riboflavin is a naturally yellow pigment, and excess amounts are excreted directly. Beets and blackberries can produce a reddish or pinkish tinge, a harmless condition sometimes called beeturia. Asparagus does not typically change color but produces a distinctive sulfurous odor in many people’s urine. Certain medications like the antibiotic nitrofurantoin can turn urine dark brown or rust-colored, and the pain reliever phenazopyridine produces a vivid orange.
What makes DIM’s color change distinctive is its mechanism. B vitamins color urine because they are themselves pigmented. Beet pigments pass through relatively intact. DIM’s metabolites are created by your liver’s enzyme activity on indole compounds, so the color is a byproduct of metabolism rather than just a pigment passing through your digestive tract. This distinction is mostly academic from a practical standpoint, since the outcome is the same: harmless, temporary color change that stops when you stop the supplement. But it does explain why the color from DIM is darker and more amber-brown rather than the vivid yellows and pinks produced by vitamins and plant pigments.
The Odor Question
Many DIM users also report a change in urine odor, not just color. This is less well-documented in clinical trials than the color change, likely because odor is harder to measure objectively and researchers tend to focus on more clinically relevant outcomes. But the chemistry makes sense. When your liver processes a surge of indole-derived compounds, the sulfate-conjugated metabolites excreted in urine carry a slightly different chemical profile than your baseline. Some users describe the odor as sharper or more pungent, while others barely notice it. As with the color change, hydration dilutes the metabolites and makes any odor less pronounced. If you drink plenty of water throughout the day, the odor difference tends to fade into the background.
The odor, like the color, tends to be most noticeable when urine is most concentrated. It does not indicate kidney stress or any pathology specific to DIM. But if urine develops a foul, unusually sweet, or ammonia-heavy smell that persists regardless of DIM use or hydration, those are worth investigating for other causes, since certain infections and metabolic conditions have characteristic urine odors.
Dose, Timing, and How Long It Lasts
The degree of urine color change correlates loosely with the dose of DIM you take. Most commercial DIM supplements are sold in doses between 100 mg and 300 mg per capsule. At lower doses, some people notice the color change and others do not. At higher doses, it becomes more common and more pronounced. The pharmacokinetic data on absorption-enhanced DIM formulations showed that the compound is well tolerated up to 200 mg in single doses, with mild side effects appearing at 300 mg in some individuals.4Cancer Epidemiology, Biomarkers & Prevention. Single-Dose Pharmacokinetics and Tolerability of Absorption-Enhanced 3,3′-Diindolylmethane in Healthy Subjects
If you stop taking DIM, the urine color change typically resolves within a day or two, depending on how quickly your body clears the remaining metabolites. DIM has a relatively short half-life in the body, so once you stop supplying new material for your liver to process, the pigmented metabolites in your urine drop off fairly quickly. This can actually serve as a useful self-test: if you stop DIM for two or three days and the color persists, something else is causing it, and you should look into other explanations.
Timing of doses relative to meals can also influence the intensity. DIM is fat-soluble and absorbs better with food, so taking it with a meal that contains some fat increases absorption. Higher absorption means more metabolites to process and excrete, which can mean a more noticeable color change. Some users find that splitting their dose across two meals rather than taking one large dose produces a less dramatic color shift, simply because the liver handles a smaller load at any given time.