If you’ve been worrying about a friend, family member, or loved one who could be abusing heroin, you’re facing an uphill battle, starting with knowing for sure whether or not the abuse is happening. Drug users almost always have keeping their addiction a secret as one of their prime directives. They are rarely honest about what they are abusing, or how much.

It’s unfortunate, but this can put you in the role of investigator. You may not be a professional detective, but now it’s on you to search for the signs of heroin abuse. But how can you tell if someone is on heroin? This is probably an accusation you want to be very sure about.

Heroin is usually snorted, smoked, or injected. Depending on how the person is using it, you are likely to find leftover evidence of drugs or paraphernalia that go along with drugs. Heroin itself can look many different ways, ranging from an off-white powder or crumbs to a dark brown or almost black sticky substance, in the case of black tar heroin.

It is common to find syringes used for injecting drugs when a friend or loved one is using heroin. You might also find small metal or glass pipes for smoking, or even homemade smoking devices made from sturdy tubes (like a plastic pen case). A person who is injecting heroin first dissolves it for use; this is what they need their “works” for, paraphernalia like dirty spoons and lighters. Injectable drug users also need to be able to find a vein readily, so watch for items that can be used as a tourniquet, such as belts, rubber tubing, or even shoelaces.

Perhaps one of the biggest telltale signs of heroin use, however, is track marks.

Heroin Track Marks

Injecting drugs is extremely dangerous. Drugs that you inject enter your system rapidly, causing the most intense possible high, immediately. This means that injecting drugs is often very popular among seasoned users, for whom snorting or smoking is no longer enough.

Although we think of intravenous drug use when we think of injected drugs, not everyone who injects drugs injects them directly into veins. Some inject drugs subcutaneously or into the muscle instead. Of course, intravenous injection or IV drug use is the quickest, most intense way to receive that high, so many users end up with the habit in the end. When they do inject into veins, they create track marks.

The veins in the crook of the arm are most frequently used for injecting drugs, so that’s the first place to look for track marks. However, other locations are possible. Look for injection marks in the non-dominant arm, since most users inject with the hand they write with. Some people may have help from a fellow user so they can use both arms and other locations.

Some other locations that are popular among drug users include the hands, legs, feet, and groin. Many users switch locations and sides to more readily hide track marks. Others might find existing injection sites becoming too scarred or inflamed to use, forcing them to switch.

What Do Heroin Track Marks Look Like?

Many commonly abused drugs can be administered via IV injection—not just heroin. Commonly injected drugs include:

  • Cocaine and crack
  • Ketamine or special K
  • Heroin
  • Morphine
  • Methamphetamine, crystal, glass
  • PCP
  • Opioid painkillers
  • Prescription stimulants such as Adderall

Drug abusers may also mix drugs and inject them together. For example, cocaine and heroin injected together is called a speedball—an uncertain experiment every time, even for experienced users. Add in potent opioids to a classic speedball, as so many current users are doing, and you are much more likely to see an overdose or even a fatality.

Perhaps one of the most telltale signs of a serious drug abuser, track marks are the scars which are left behind after injecting drugs. These track marks are caused by a range of factors, but here are the three most common causes:

  • Chronic abuse. Repeated and prolonged abuse at the same injection site makes you more likely to develop track marks. Over time, as that same location gets used for injecting drugs over and over again, a person continuously damages the vein, causing scars to form and build up.
  • Old, dull needles. Needles that are used repeatedly become dull and blunted. If they are used anyway to inject drugs, this damages the vein, placing excess pressure on it.
  • Impure drugs. Street drugs are not pure, and each one is a little different. They are cut with different compounds and manufactured in different ways, which means they all contain different impurities and contaminants. These toxins build up in the body, and cause discoloration of the track mark scar.

While track marks are one of the best and clearest signs that a person is abusing injectable drugs, looking for them can be tricky. Because different factors play a part in the formation of track marks, they can look very different from person to person, and even in the same person over time. Depending on which healing stage they’re in, an addict’s track marks might look very different than they used to; in fact, the same person might have many old scars interspersed with fresh track marks.

Still, there are some specific things to look for:

  • Recent marks. Recent track marks are fresh looking lesions, unhealed sores. They look at first like just what they are: puncture marks. They can also resemble bruises or scabs, like what you might see after a blood draw.
  • Old marks. Over time, an addict’s drug use advances. This causes the skin at injection sites to bleed, crack, and become infected. You can sometimes see scarring and individual track marks along the length of the vein; these places look a little darker usually and appear slightly raised compared to other areas of skin.
  • Hiding injection sites. Another tell-tale sign with track marks is hiding them. When it’s a hot July and your friend or loved one is wearing long sleeves, long pants, and closed shoes all of the time no matter what, they may be hiding something like track marks. Some longtime drug abusers even get tattoos to cover track marks (although this is not a wise move if the skin is already damaged).

Track marks can last for years of time after an addict stops using, unfortunately, so seeing them doesn’t mean that someone is using right now. Still, it’s a good thing to know what track marks look like, how they’re caused, and how to get help when you spot heroin track marks.